/* ============================================================
   GEN CHEM INTERACTIVES: COMPONENTS (chem only)
   Everything the shared runtime (public/textbook/base.css and lesson.css)
   defines is gone from this file. What is left is chem's own: particle
   diagrams and the Bohr model, the periodic-table grid, the Reference Center
   drawer, the dashboard, the practice bridge, the resume bar, the Socratic
   companion, and the lesson-only layouts of the building tools.

   Every simulation runs on the shared sim shell; each unit's tool rules are in
   the "UNIT n TOOLS" sections at the end.
   Zero em-dashes.
   ============================================================ */

/* ---- chem tokens that are not in the standard ----
   --text-2xs (11px) is legal only inside a diagram or canvas; --text-3xs (9px)
   only in the periodic-table grid (standard 2.1). */
:root {
  --text-2xs: 0.6875rem;
  --text-3xs: 0.5625rem;
}

/* ---- small utilities ---- */
.chem { font-family: var(--mono); }
/* a script recolours status badges with this */
.label-accent { color: var(--accent); }
/* Quick Check and Cram View fold sections away with this class */
.is-folded { display: none !important; }
/* a short mono line under a figure or a table, such as a source note */
.fine-print { font-family: var(--mono); font-size: var(--text-xs); letter-spacing: 0.04em; color: var(--ink-mute); }

/* ---- small caption helpers: colour a legend glyph the way the diagram colours it ---- */
.cap-valence { color: var(--accent); }
.cap-core { color: var(--ink-mute); }
.cap-gap { display: inline-block; width: 0.5em; height: 0.5em; border: 1px dashed var(--accent); border-radius: 50%; vertical-align: middle; }

/* ---- sim legend swatches for chem's own tokens (the shared file covers accent, good, bad, warn, cool, ink) ---- */
.sim-legend .key[data-token="ink-mute"] { border-color: var(--ink-mute); }
.sim-legend .key[data-shape="dot"][data-token="ink-mute"] { background: var(--ink-mute); }
.sim-legend .key[data-token="nucleus"] { border-color: var(--nucleus); }
.sim-legend .key[data-shape="dot"][data-token="nucleus"] { background: var(--nucleus); }
.sim-legend .key[data-token="paper-3"] { border-color: var(--ink-mute); }
.sim-legend .key[data-shape="dot"][data-token="paper-3"] { background: var(--paper-3); }
.sim-legend .key[data-token="water"] { border-color: var(--water); }
.sim-legend .key[data-shape="dot"][data-token="water"] { background: var(--water); }

/* ---- the practice card at the end of every lesson ---- */
.practice-card {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
  padding: 1.5rem;
  background: var(--card);
  border: 1.5px solid var(--accent);
  border-radius: var(--r-card);
}
.practice-card-head { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 0.5rem; }
.practice-card-note { font-family: var(--mono); font-size: var(--text-xs); color: var(--ink-mute); }
.practice-card h3 { margin: 0; font-size: var(--text-md); }
.practice-card p { margin: 0; font-size: var(--text-sm); line-height: 1.5; color: var(--ink-soft); }

/* ---- a figure caption inside a group of diagrams (the shared figcaption covers a lone figure) ---- */
.diagram-cap { margin-top: 0.6rem; font-family: var(--mono); font-size: var(--text-sm); line-height: 1.45; color: var(--ink-soft); text-align: center; }

/* ---- the closing line of a lesson ---- */

/* ============================================================
   GEN CHEM INTERACTIVES - COMPONENTS
   The shared component library. Every lesson inherits these.
   Lesson-specific styling should be rare; prefer extending here.
   ============================================================ */
/* Prominent display equation / reaction block with tabular numbers and clean layout */
.chem-display {
  font-family: var(--mono);
  font-size: clamp(var(--text-md), 2.5vw, var(--text-xl));
  font-weight: 600;
  color: var(--ink);
  display: block;
  text-align: center;
  padding: 1.25rem 0;
  letter-spacing: 0.02em;
  line-height: 1.6;
}
.chem-display em {
  font-style: normal;
  font-weight: 600;
  color: var(--ink);
}
.chem-display .accent-term {
  color: var(--accent);
}
.sim-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
  margin-bottom: 1.5rem;
}
@media (max-width: 768px) {
  .sim-grid {
    grid-template-columns: 1fr;
  }
}
/* ---- resume bar (offered, never automatic; top offset set in core.js) ---- */
.resume-bar{position:fixed;left:0;right:0;z-index:58;display:flex;align-items:center;justify-content:space-between;gap:.75rem;
  padding:.55rem var(--gutter);background:var(--card);border-bottom:1px solid var(--hair);
  transform:translateY(-100%);opacity:0;transition:transform .3s cubic-bezier(.22,1,.36,1),opacity .3s ease;}
.resume-bar.in{transform:none;opacity:1;}
.resume-bar-text{font-family:var(--display);font-size:var(--text-sm);color:var(--ink-soft);min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;}
.resume-bar-text b{color:var(--ink);font-weight:600;}
.resume-bar-actions{display:flex;align-items:center;gap:.4rem;flex-shrink:0;}
.resume-bar-btn{height:30px;padding:0 .8rem;border:1px solid var(--accent);background:transparent;color:var(--accent);cursor:pointer;
  border-radius:4px;font-family:var(--mono);font-size:var(--text-xs);letter-spacing:.12em;text-transform:uppercase;transition:all .2s ease;}
.resume-bar-btn:hover{background:var(--accent);color:var(--card);}
.resume-bar-dismiss{height:30px;width:30px;border:1px solid var(--hair);background:transparent;color:var(--ink-mute);cursor:pointer;
  border-radius:4px;font-size:var(--text-md);line-height:1;transition:all .2s ease;}
.resume-bar-dismiss:hover{color:var(--accent);border-color:var(--accent);}
@media (max-width:600px){
  .resume-bar{padding:.5rem .75rem;}
  .resume-bar-text{font-size:var(--text-xs);}
}
@media (prefers-reduced-motion:reduce){
  .resume-bar{transition:none;}
}
.step.bullet{display:flex;gap:.85rem;align-items:baseline;color:var(--ink-soft);}
.step.bullet::before{content:'';flex:0 0 8px;height:8px;background:var(--accent);margin-top:.55em;}
.step.bullet p{max-width:none;}
.levers{display:grid;grid-template-columns:1fr;gap:1rem;margin-top:1.85rem;}
@media(min-width:720px){.levers{grid-template-columns:1fr 1fr;}}
.lever{background:var(--card);border:1px solid var(--hair);padding:1.5rem 1.6rem;}
.lever .arrow{font-family:var(--mono);font-size: var(--text-2xl);color:var(--accent);font-weight:600;}
.lever .lever-symbol-wrap{display:flex;align-items:center;gap:.75rem;margin-bottom:.5rem;}
.lever .lever-symbol{font-family:var(--mono);font-size: var(--text-3xl);color:var(--accent);font-weight:700;line-height:1;}
.lever .lever-symbol-sub{font-family:var(--mono);font-size: var(--text-xs);letter-spacing:.04em;color:var(--ink-mute);text-transform:uppercase;}
.lever h4{margin:.45rem 0 .65rem;}
.lever p{font-size: var(--text-base);color:var(--ink-soft);max-width:none;}
/* ---- expandable dense block ---- */
.more-wrap{margin-top:1rem;}
.more-toggle{font-family:var(--mono);font-size: var(--text-xs);letter-spacing:.1em;text-transform:uppercase;color:var(--accent);background:transparent;border:none;border-bottom:1px solid var(--accent-soft);cursor:pointer;padding:.2rem 0;}
/* ============ SHARED INTERACTIVE FRAME ============
   Every interactive - Bohr builder, trend explorer, BCA table,
   equation balancer, graph - lives in this same frame.
   .interactive  → bordered card
   .interactive-head → mono label (+ optional tabs)
   .readout → result/explanation panel
   ================================================== */
.interactive{background:var(--card);border:1px solid var(--hair);padding:clamp(1.1rem,3vw,2rem);margin-top:1.6rem;}
.interactive-head{display:flex;align-items:baseline;justify-content:space-between;gap:1rem;flex-wrap:wrap;margin-bottom:1.25rem;}
.interactive-head .label{color:var(--accent);}
/* prose lists inside an interactive card. tokens.css resets padding to 0 on
   everything, which pulls list markers out to the text column's left edge and
   reads as unindented - restore a hanging indent. Lists that set their own
   padding-left inline (the branch/ion cards) keep it; inline wins. */
.interactive ul,.interactive ol{padding-left:1.75rem;margin:.7rem 0 1.1rem;}
.interactive li{margin-bottom:.4rem;}
.interactive li:last-child{margin-bottom:0;}
.tabs{display:flex;flex-wrap:wrap;gap:.5rem;}
.tab{font-family:var(--mono);font-size: var(--text-xs);letter-spacing:.05em;text-transform:uppercase;padding:.58rem .9rem;background:transparent;color:var(--ink-soft);border:1px solid var(--hair);cursor:pointer;transition:all .18s ease;min-height:42px;}
.tab:hover{border-color:var(--accent);color:var(--accent);}
.tab.active{background:var(--ink);color:var(--paper);border-color:var(--ink);}
.result-panel{border:1px solid var(--hair);background:var(--paper);padding:1.25rem 1.4rem;}
.result-panel .label{margin-bottom:.6rem;}
.result-panel h4{color:var(--accent);margin-bottom:.5rem;}
.result-panel p{font-size: var(--text-base);color:var(--ink-soft);max-width:none;}
.result-panel .dirs{display:flex;gap:1.4rem;margin-top:.9rem;flex-wrap:wrap;}
.result-panel .dir{font-family:var(--mono);font-size: var(--text-xs);color:var(--ink);}
.result-panel .dir span{color:var(--accent);font-weight:600;}
/* ---- atom / Bohr diagram (reusable atomic-level component) ---- */
.atom-stage{display:grid;grid-template-columns:1fr;gap:1.3rem;align-items:center;}
@media(min-width:820px){.atom-stage{grid-template-columns:1fr 1fr;}}
.atom-svg-wrap{display:flex;flex-direction:column;align-items:center;width:100%;}
.atom-shell{fill:none;stroke:var(--shell);stroke-width:1;}
.atom-nucleus{fill:var(--nucleus);}
.atom-nuc-label{fill:#fff;font-family:var(--mono);font-weight:600;}
.atom-e{fill:var(--electron);}
.atom-controls{display:flex;align-items:center;gap:.8rem;margin-top:1rem;}
.atom-controls .step-btn{width:42px;height:42px;border:1px solid var(--hair);background:var(--card);color:var(--ink);font-family:var(--display);font-size: var(--text-lg);font-weight:700;cursor:pointer;transition:all .18s ease;}
.atom-controls .step-btn:hover:not(:disabled){border-color:var(--accent);color:var(--accent);}
.atom-controls .step-btn:disabled{opacity:.3;cursor:not-allowed;}
.step-readout-el{font-family:var(--display);font-weight:700;font-size: var(--text-md);min-width:8.5rem;text-align:center;}
.step-readout-el span{font-family:var(--mono);font-weight:500;font-size: var(--text-xs);color:var(--ink-mute);display:block;text-transform:uppercase;letter-spacing:.1em;margin-top:.15rem;}
.atom-stats{display:flex;gap:1.5rem;margin-top:.6rem;font-family:var(--mono);font-size: var(--text-sm);color:var(--ink-soft);}
.atom-stats b{color:var(--accent);}
/* ---- periodic table heat-map (reusable component) ---- */
.ptable-scroll{overflow-x:auto;padding-bottom:.5rem;}
.ptable{display:grid;grid-template-columns:repeat(2,1fr) .45fr repeat(6,1fr);gap:4px;min-width:520px;}
.pcell{aspect-ratio:1/1;border:1px solid var(--hair-soft);position:relative;display:flex;flex-direction:column;align-items:center;justify-content:center;background:var(--card);transition:background .35s ease,transform .12s ease;color:var(--ink);user-select:none;overflow:hidden;}
.pcell.has-data{cursor:pointer;}
.pcell.has-data:hover{transform:scale(1.1);z-index:5;border-color:var(--ink);}
.pcell .sym{font-family:var(--display);font-weight:800;font-size: clamp(var(--text-xs), 1.8vw, var(--text-md));line-height:1;}
.pcell .z{font-family:var(--mono);font-size: var(--text-3xs);position:absolute;top:2px;left:3px;opacity:.7;}
.pcell .val{font-family:var(--mono);font-weight:500;font-size: clamp(var(--text-3xs), 1.3vw, var(--text-xs));opacity:.95;margin-top:2px;}
.pcell.spacer{visibility:hidden;}
.pcell.dim{opacity:.3;}
.pcell.selected{outline:2px solid var(--accent);outline-offset:-2px;z-index:4;}
.legend{display:flex;align-items:center;justify-content:center;gap:1.5rem;margin-top:1.2rem;font-family:var(--mono);font-size: var(--text-2xs);letter-spacing:.07em;text-transform:uppercase;color:var(--ink-mute);flex-wrap:wrap;}
.legend .bar{height:11px;width:130px;border:1px solid var(--hair);}
.legend .swatch{display:inline-flex;align-items:center;gap:.5rem;}
.legend .chip{width:13px;height:13px;min-height:0;padding:0;display:inline-block;flex-shrink:0;border:1px solid var(--hair);cursor:default;}
.explorer-grid{display:grid;grid-template-columns:1fr;gap:1.25rem;margin-top:1.5rem;}
@media(min-width:860px){.explorer-grid{grid-template-columns:1.25fr 1fr;align-items:start;}}
.cmp-hint{font-family:var(--mono);font-size: var(--text-xs);color:var(--ink-mute);}
.cmp-out{margin-top:.75rem;font-family:var(--serif);font-style:italic;font-size: var(--text-base);color:var(--ink);min-height:1.5em;}
.cmp-out b{font-style:normal;font-family:var(--display);font-weight:700;color:var(--accent);}
.opt{text-align:left;padding:.95rem 1.15rem;background:var(--card);border:1px solid var(--hair);cursor:pointer;font-family:var(--display);font-weight:500;font-size: var(--text-base);color:var(--ink);transition:all .18s ease;min-height:48px;}
.opt:hover{border-color:var(--accent);}
.opt .ltr{display:block;font-family:var(--mono);font-size: var(--text-2xs);letter-spacing:.14em;color:var(--ink-mute);margin-bottom:.3rem;}
.opt.correct{border-color:var(--good);border-width:2px;background:color-mix(in srgb,var(--good) 12%,transparent);}
.opt.wrong{border-color:var(--accent);background:color-mix(in srgb,var(--accent) 10%,transparent);opacity:.8;}
.recall-section{background:var(--paper-2);border-top:1px solid var(--hair-soft);border-bottom:1px solid var(--hair-soft);}
/* Option cards & choices (.opt and .btn.opt) */
.btn.opt, .opt{text-align:left;padding:.95rem 1.15rem;background:var(--card);border:1px solid var(--hair);cursor:pointer;font-family:var(--display);font-weight:500;font-size: var(--text-base);color:var(--ink);transition:all .18s ease;min-height:48px;text-transform:none;letter-spacing:normal;border-radius:4px;}
.btn.opt:hover, .opt:hover{border-color:var(--accent);background:var(--paper-2);color:var(--ink);}
.btn.opt.correct, .opt.correct{border-color:var(--good)!important;border-width:2px;background:color-mix(in srgb,var(--good) 12%,var(--card))!important;color:var(--good)!important;}
.btn.opt.wrong, .opt.wrong{border-color:var(--accent)!important;background:color-mix(in srgb,var(--accent) 10%,var(--card))!important;color:var(--accent)!important;opacity:.9;}
/* Form Selects / Dropdowns - prevents uppercase cascade and ensures high dark mode contrast */
.form-select, select.btn, select.step-select, .builder-panel select {
  font-family: var(--display);
  font-size: var(--text-base);
  color: var(--ink);
  background: var(--card);
  border: 1px solid var(--hair);
  border-radius: 4px;
  padding: 0.55rem 0.85rem;
  text-transform: none !important;
  letter-spacing: normal !important;
  outline: none;
  cursor: pointer;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
  min-height: 42px;
}
.form-select:focus, select.btn:focus, select.step-select:focus, .builder-panel select:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 2px color-mix(in srgb, var(--accent) 25%, transparent);
}
/* Dark mode overrides for buttons, form controls, and options */
:root.dark .btn.opt, :root.dark .opt { background: var(--card); color: var(--ink); border-color: rgba(231,237,230,0.2); }
:root.dark .btn.opt:hover, :root.dark .opt:hover { background: var(--paper-2); border-color: var(--accent); }
:root.dark .form-select, :root.dark select.btn, :root.dark select.step-select, :root.dark .builder-panel select {
  background: var(--card);
  color: var(--ink);
  border-color: rgba(231,237,230,0.25);
}
:root.dark select option { background: var(--card); color: var(--ink); }
/* self-explain */
.selfx-mark{border-left:2px solid var(--accent);padding-left:1.25rem;margin:1rem 0 .6rem;}
.selfx-mark p{font-family:var(--serif);font-style:italic;font-size: clamp(var(--text-lg), 2.5vw, var(--text-2xl));color:var(--ink);max-width:none;}
/* ---- footer ---- */
.footer{text-align:center;padding:2.75rem var(--gutter) 3.5rem;border-top:1px solid var(--hair-soft);background:var(--paper-3);}
.footer .label{color:var(--ink-mute);}
.footer p{font-family:var(--serif);font-style:italic;color:var(--ink-soft);max-width:none;margin-top:.5rem;}
/* ============ PARTICLE-DIAGRAM CONVENTIONS ============
   Adheres to the class poster set. Reuse these classes for any
   particle / container / energy diagram so they stay consistent.
   particle = filled circle (.d-particle) ; metal = square (.d-metal)
   framing  = dashed box (.d-frame) ; container = solid walls (.d-wall)
   water    = blue wavy line (.d-water)
   motion   = brackets(solid) / lumps(liquid) / tails(gas) drawn per-lesson
   ALWAYS include a legend; ALWAYS conserve particles before/after.
   ====================================================== */
/* High-Resolution Photography & Macro Figures */
.figure.photo {
  border-radius: 8px;
  overflow: hidden;
  background: var(--card);
  border: 1px solid var(--hair);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.06);
}
.figure.photo img,
.figure.photo picture {
  width: 100%;
  height: auto;
  display: block;
  border-radius: 6px 6px 0 0;
}
.figure.photo .diagram-cap,
.figure.photo figcaption {
  padding: 0.75rem 1rem;
  font-family: var(--display);
  font-size: var(--text-sm);
  color: var(--ink-soft);
  background: var(--card);
  border-top: 1px solid var(--hair);
  line-height: 1.5;
  text-align: left;
}
:root.dark .figure.photo {
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.35);
  border-color: var(--hair);
}
/* Macro-Micro Comparative Grid */
.macro-micro-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
  align-items: stretch;
  margin: 1.75rem 0;
}
@media (max-width: 768px) {
  .macro-micro-grid {
    grid-template-columns: 1fr;
  }
}
.macro-micro-cell {
  display: flex;
  flex-direction: column;
  background: var(--card);
  border: 1px solid var(--hair);
  border-radius: 8px;
  overflow: hidden;
}
.macro-micro-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 0.75rem;
  font-family: var(--mono);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  background: var(--paper-2);
  border-bottom: 1px solid var(--hair);
  color: var(--ink);
}
.macro-micro-body {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}
.macro-micro-body img {
  width: 100%;
  height: auto;
  display: block;
  border-radius: 4px;
}
.macro-micro-caption {
  padding: 0.6rem 0.85rem;
  font-family: var(--display);
  font-size: var(--text-xs);
  color: var(--ink-mute);
  border-top: 1px solid var(--hair);
  line-height: 1.45;
}
.d-particle{fill:var(--electron);stroke:var(--ink);stroke-width:1.2;}
/* SVG geometry attributes cannot take var() - a circle written as
   r="var(--dia-r-*)" fails attribute parsing and collapses to r=0
   (invisible). The CSS `r` property DOES accept var(), and CSS wins
   over the presentation attribute, so re-apply the radius here.
   Tokens are unitless; in SVG, 1px = 1 user unit. */
circle[r="var(--dia-r-particle)"]{r:calc(var(--dia-r-particle) * 1px);}
circle[r="var(--dia-r-atom-sm)"]{r:calc(var(--dia-r-atom-sm) * 1px);}
circle[r="var(--dia-r-atom)"]{r:calc(var(--dia-r-atom) * 1px);}
.d-metal{fill:var(--ink-mute);stroke:var(--ink);stroke-width:1.2;}
.d-shell{fill:none;stroke:var(--shell);stroke-width:0.8;}
.d-nuc{fill:var(--nucleus);}
.d-nuc-t{fill:#fff;font-family:var(--mono);font-weight:600;font-size: var(--text-3xs);}
.d-frame{fill:none;stroke:var(--ink-mute);stroke-width:1.5;stroke-dasharray:6 4;}
.d-wall{fill:none;stroke:var(--ink);stroke-width:2.2;stroke-linecap:round;stroke-linejoin:round;}
.d-water{fill:none;stroke:var(--water);stroke-width:1.8;}
.d-arrow{stroke:var(--ink);stroke-width:1.6;}
/* NOTE: for colored arrows set stroke INLINE and omit this class (class wins over attribute) */
.d-label{font-family:var(--display);font-weight:600;fill:var(--ink);}
.d-sub{font-family:var(--mono);fill:var(--ink-mute);}
/* ---- Global SVG Diagram Typography & Contrast Engine ---- */
/* Base fallback: any text without a fill defaults to --ink */
svg text:not([fill]),
svg text[fill="currentColor"],
svg text[fill="inherit"],
svg text[fill="var(--ink)"],
svg text[fill="var(--ink)"] {
  fill: var(--ink);
}
svg text[fill="var(--ink-soft)"] {
  fill: var(--ink-soft);
}
svg text[fill="var(--ink-mute)"] {
  fill: var(--ink-mute);
}
svg text[fill="var(--accent)"] {
  fill: var(--accent);
}
svg text[fill="var(--good)"],
svg text[fill="var(--good)"] {
  fill: var(--good);
}
svg text[fill="var(--warn)"] {
  fill: var(--warn);
}
svg text[fill="var(--card)"] {
  fill: var(--card);
}
svg text[fill="var(--paper)"] {
  fill: var(--paper);
}
/* Any tspan without fill inherits its parent text fill */
svg tspan:not([fill]) {
  fill: inherit;
}
/* Dark mode overrides for hardcoded black/dark text, tspans, strokes, and marker paths */
:root.dark svg text[fill="#000"],
:root.dark svg text[fill="#000000"],
:root.dark svg text[fill="black"],
:root.dark svg text[fill="#111"],
:root.dark svg text[fill="#111111"],
:root.dark svg text[fill="#16201C"],
:root.dark svg text[fill="#222"],
:root.dark svg text[fill="#222222"],
:root.dark svg text[fill="#333"],
:root.dark svg text[fill="#333333"],
:root.dark svg text[fill="#1a1a1a"],
:root.dark svg text[fill="#2a2a2a"],
:root.dark svg text[fill="#1e293b"],
:root.dark svg text[fill="#334155"],
:root.dark svg text[fill="#0f172a"] {
  fill: var(--ink) !important;
}
:root.dark svg tspan[fill="#000"],
:root.dark svg tspan[fill="#000000"],
:root.dark svg tspan[fill="black"],
:root.dark svg tspan[fill="#16201C"],
:root.dark svg tspan[fill="#111"],
:root.dark svg tspan[fill="#222"],
:root.dark svg tspan[fill="#333"] {
  fill: var(--ink) !important;
}
:root.dark svg line[stroke="#000"],
:root.dark svg line[stroke="#000000"],
:root.dark svg line[stroke="black"],
:root.dark svg line[stroke="#16201C"],
:root.dark svg line[stroke="#111"],
:root.dark svg line[stroke="#222"],
:root.dark svg line[stroke="#333"],
:root.dark svg path[stroke="#000"],
:root.dark svg path[stroke="#000000"],
:root.dark svg path[stroke="black"],
:root.dark svg path[stroke="#16201C"],
:root.dark svg path[stroke="#111"],
:root.dark svg path[stroke="#222"],
:root.dark svg path[stroke="#333"],
:root.dark svg rect[stroke="#000"],
:root.dark svg rect[stroke="#000000"],
:root.dark svg rect[stroke="black"],
:root.dark svg rect[stroke="#16201C"],
:root.dark svg circle[stroke="#000"],
:root.dark svg circle[stroke="#000000"],
:root.dark svg circle[stroke="black"],
:root.dark svg circle[stroke="#16201C"] {
  stroke: var(--ink) !important;
}
:root.dark svg marker path[fill="#000"],
:root.dark svg marker path[fill="#000000"],
:root.dark svg marker path[fill="black"],
:root.dark svg marker path[fill="#16201C"] {
  fill: var(--ink) !important;
}
/* ---- Bohr configuration builder (reusable atomic component) ----
   Valence electrons drawn in the accent; everything else in the
   electron color, so "the ones that do chemistry" read at a glance. */
.atom-e-val{fill:var(--accent);stroke:var(--ink);stroke-width:1;}
.builder-side{display:flex;flex-direction:column;gap:1rem;}
.config-out{border:1px solid var(--hair);background:var(--paper);padding:1.1rem 1.3rem;}
.config-out .label{margin-bottom:.6rem;}
.config-shells{font-family:var(--mono);font-weight:600;font-size: clamp(var(--text-xl), 4.5vw, var(--text-2xl));letter-spacing:.02em;color:var(--ink);}
.config-shells .vshell{color:var(--accent);}
.config-shells .sep{color:var(--ink-mute);font-weight:400;}
.valence-pill{margin-top:.75rem;font-family:var(--mono);font-size: var(--text-xs);letter-spacing:.04em;color:var(--ink-soft);}
.valence-pill b{color:var(--accent);font-weight:600;}
.jump-chips{display:flex;flex-wrap:wrap;gap:.4rem;}
.jump-chips .chip{font-family:var(--mono);font-size: var(--text-xs);font-weight:500;padding:.4rem .65rem;background:transparent;border:1px solid var(--hair);color:var(--ink-soft);cursor:pointer;min-height:36px;transition:all .15s ease;}
.jump-chips .chip:hover{border-color:var(--accent);color:var(--accent);}
.chip.active{background:var(--ink);color:var(--paper);border-color:var(--ink);}
/* ---- configuration self-test (retrieval on the exact skill) ---- */
.selftest{display:grid;gap:1.25rem;}
.st-prompt{border-left:3px solid var(--accent);padding-left:1.15rem;}
.st-prompt h3{margin:.15rem 0 .25rem;}
.st-prompt .st-meta{font-family:var(--mono);font-size: var(--text-sm);color:var(--ink-mute);}
.st-fields{display:grid;grid-template-columns:1fr;gap:1rem;}
@media(min-width:600px){.st-fields{grid-template-columns:2fr 1fr;}}
.st-fields label{font-family:var(--mono);font-size: var(--text-xs);letter-spacing:.08em;text-transform:uppercase;color:var(--ink-mute);display:flex;flex-direction:column;gap:.45rem;}
.st-fields input{font-family:var(--mono);font-size: var(--text-lg);padding:.8rem 1rem;background:var(--card);border:1px solid var(--hair);color:var(--ink);outline:none;transition:border-color .2s ease,color .2s ease;border-radius:6px;}
.st-fields input:focus{border-color:var(--accent);}
.st-fields input.correct{border-color:var(--good);color:var(--good);}
.st-fields input.wrong{border-color:var(--accent);color:var(--accent);}
/* ---- shell-filling order strip (the K→Ga wrinkle) ---- */
.fill-order{display:grid;gap:.7rem;margin:1.6rem 0;}
.fo-row{border:1px solid var(--hair);background:var(--card);padding:.85rem 1.15rem;}
.fo-head{display:flex;align-items:baseline;gap:1rem;}
.fo-el{font-family:var(--display);font-weight:700;font-size: var(--text-md);min-width:6.5rem;}
.fo-cfg{font-family:var(--mono);font-size: var(--text-md);color:var(--ink-soft);}
.fo-cfg b{color:var(--accent);font-weight:600;}
.fo-note{font-size: var(--text-base);color:var(--ink-mute);margin-top:.4rem;max-width:none;}
/* Dark mode backing for transparent PNG/SVG images with dark text */
:root.dark .diagram:not(.photo) img:not(.photo-img),
:root.dark .figure:not(.photo) img:not(.photo-img),
:root.dark .d-frame img:not(.photo-img),
:root.dark .synopsis-figure img:not(.photo-img),
:root.dark .lightbox-content img:not(.photo-img),
:root.dark img.dark-backed {
  background-color: #ffffff;
  padding: 0.5rem;
  border-radius: 6px;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.4);
}
:root.dark .figure.photo img,
:root.dark img.photo-img,
:root.dark .lightbox-content img.photo-img {
  background-color: transparent !important;
  padding: 0 !important;
  box-shadow: none !important;
}
/* ---- Textbook Bridge (Practice & Simulation Integration) ---- */
.textbook-bridge {
  margin: 3.5rem auto 2.5rem;
  padding: 1.75rem;
  background: var(--card);
  border: 1px solid var(--hair-soft);
  border-radius: 12px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.03);
  font-family: var(--display);
  box-sizing: border-box;
}
.textbook-bridge-header {
  margin-bottom: 1.25rem;
}
.textbook-bridge-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.25rem 0.75rem;
  background: var(--paper-2);
  border: 1px solid var(--hair-soft);
  border-radius: 999px;
  font-family: var(--mono);
  font-size: var(--text-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-soft);
  margin-bottom: 0.65rem;
}
.bridge-badge-icon {
  font-size: var(--text-sm);
}
.textbook-bridge-title {
  font-size: var(--text-lg);
  font-weight: 800;
  color: var(--ink);
  margin: 0 0 0.35rem;
  letter-spacing: -0.01em;
}
.textbook-bridge-desc {
  font-size: var(--text-base);
  color: var(--ink-soft);
  line-height: 1.5;
  margin: 0;
}
.textbook-bridge-content {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.25rem;
  margin-top: 1.25rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--hair-soft);
}
@media(min-width: 640px) {
  .textbook-bridge-content.has-sims {
    grid-template-columns: 1fr 1fr;
  }
}
.bridge-col {
  display: flex;
  flex-direction: column;
}
.bridge-col-heading {
  font-family: var(--mono);
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  color: var(--ink-mute);
  margin: 0 0 0.75rem;
}
.bridge-btn-group {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}
.bridge-btn {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  padding: 0.75rem 1rem;
  min-height: 48px;
  border-radius: 8px;
  text-decoration: none;
  background: var(--paper-2);
  border: 1px solid var(--hair-soft);
  color: var(--ink);
  transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
  box-sizing: border-box;
}
.bridge-btn:hover {
  background: var(--paper-3);
  border-color: var(--hair);
  transform: translateY(-1px);
  box-shadow: 0 3px 8px rgba(0, 0, 0, 0.05);
}
.bridge-btn-primary {
  border-left: 3px solid var(--accent);
}
.bridge-btn-secondary {
  border-left: 3px solid var(--good);
}
.bridge-btn-sim {
  border-left: 3px solid var(--cool);
}
.bridge-btn-icon {
  font-size: var(--text-lg);
  line-height: 1;
  flex-shrink: 0;
}
.bridge-btn-text {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  min-width: 0;
}
.bridge-btn-title {
  font-size: var(--text-base);
  font-weight: 700;
  color: var(--ink);
  line-height: 1.2;
}
.bridge-btn-sub {
  font-size: var(--text-xs);
  color: var(--ink-mute);
  font-family: var(--mono);
}
.bridge-btn:hover .bridge-btn-title {
  color: var(--accent);
}
/* ---- Textbook Index Page Styles ---- */
.dashboard-header {
  padding: 4.5rem var(--gutter) 2rem;
  text-align: center;
  border-bottom: 1px solid var(--hair-soft);
}
.dashboard-header h1 {
  font-size: clamp(var(--text-2xl), 5vw, var(--text-4xl));
  font-weight: 900;
  margin-bottom: 0.75rem;
  letter-spacing: -0.03em;
}
.dashboard-header .lede {
  max-width: 38rem;
  margin: 0 auto 1.5rem;
  font-size: var(--text-md);
  line-height: 1.55;
  color: var(--ink-soft);
}
/* Search bar */
.search-container {
  max-width: 32rem;
  margin: 0 auto;
  position: relative;
  width: 100%;
}
.search-input {
  width: 100%;
  height: 48px;
  padding: 0 1.25rem 0 2.8rem;
  border: 1px solid var(--hair);
  background: var(--card);
  color: var(--ink);
  font-family: var(--display);
  font-size: var(--text-base);
  border-radius: 24px;
  outline: none;
  transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.02);
}
.search-input:focus {
  border-color: var(--accent);
  box-shadow: 0 4px 18px var(--hair-soft), 0 0 0 3px var(--accent-soft);
}
.search-icon {
  position: absolute;
  left: 1rem;
  top: 50%;
  transform: translateY(-50%);
  width: 16px;
  height: 16px;
  color: var(--ink-mute);
  pointer-events: none;
}
/* Tabs */
.dashboard-tabs-wrap {
  position: sticky;
  top: 52px;
  z-index: 50;
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--hair-soft);
  display: flex;
  justify-content: center;
  padding: 0.5rem var(--gutter);
}
.dashboard-tabs {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.4rem;
  width: 100%;
  max-width: 60rem;
}
.dashboard-tab {
  flex: 0 0 auto;
  text-align: center;
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 0.7rem 0.6rem;
  background: var(--card);
  color: var(--ink-soft);
  border: 1px solid var(--hair-soft);
  cursor: pointer;
  transition: all 0.2s ease;
  border-radius: 4px;
  white-space: nowrap;
}
.dashboard-tab:hover {
  border-color: var(--accent-soft);
  color: var(--accent);
}
.dashboard-tab.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
  font-weight: 600;
}
/* Dashboard Resources Dropdown */
.dashboard-tab-dropdown {
  position: relative;
  display: inline-block;
}
.dashboard-tab-dropdown .dropdown-trigger {
  display: flex;
  align-items: center;
  gap: 0.35rem;
}
.dashboard-tab-dropdown .dropdown-menu {
  display: none;
  position: absolute;
  top: calc(100% + 4px);
  left: 50%;
  transform: translateX(-50%);
  background: var(--paper);
  border: 1px solid var(--hair-soft);
  border-radius: 4px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.12);
  min-width: 15rem;
  z-index: 100;
  padding: 0.35rem 0;
}
.dashboard-tab-dropdown.open .dropdown-menu {
  display: flex;
  flex-direction: column;
}
.dashboard-tab-dropdown .dropdown-item {
  display: block;
  width: 100%;
  padding: 0.6rem 0.9rem;
  text-align: left;
  background: none;
  border: none;
  font-family: var(--mono);
  font-size: var(--text-xs);
  color: var(--ink-soft);
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.15s ease;
}
.dashboard-tab-dropdown .dropdown-item:hover {
  background: var(--paper-2);
  color: var(--accent);
}
.dashboard-tab-dropdown .dropdown-item.active {
  color: var(--accent);
  font-weight: 600;
  background: color-mix(in srgb, var(--accent) 8%, transparent);
}
.dashboard-tab-dropdown .dropdown-divider {
  height: 1px;
  background: var(--hair-soft);
  margin: 0.35rem 0;
}
/* View Mode Switcher (By Unit vs By PE) */
.view-mode-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.75rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--hair-soft);
  flex-wrap: wrap;
  gap: 0.75rem;
}
.view-mode-meta {
  font-family: var(--mono);
  font-size: var(--text-xs);
  color: var(--ink-soft);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.view-toggle-group {
  display: inline-flex;
  background: var(--paper-2);
  padding: 3px;
  border-radius: 6px;
  border: 1px solid var(--hair-soft);
  gap: 2px;
}
.view-toggle-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--mono);
  font-size: var(--text-xs);
  padding: 0.4rem 0.75rem;
  border: none;
  background: transparent;
  color: var(--ink-soft);
  cursor: pointer;
  border-radius: 4px;
  transition: all 0.15s ease;
  white-space: nowrap;
}
.view-toggle-btn:hover {
  color: var(--ink);
}
.view-toggle-btn.active {
  background: var(--card);
  color: var(--accent);
  font-weight: 600;
  box-shadow: 0 1px 3px rgba(0,0,0,0.08);
}
/* Dashboard Panel Visibility */
.dashboard-panel {
  display: none;
  animation: fadeIn 0.3s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}
.dashboard-panel.active {
  display: block;
}
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: none; }
}
/* Unit Headers */
.unit-section {
  margin-top: 3rem;
  margin-bottom: 4rem;
}
.unit-section h2 {
  font-size: var(--text-xl);
  font-weight: 800;
  color: var(--ink-soft);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  border-bottom: 2px solid var(--ink);
  padding-bottom: 0.4rem;
  margin-bottom: 1.8rem;
  display: flex;
  justify-content: space-between;
  align-items: baseline;
}
.unit-section h2 span {
  font-family: var(--mono);
  font-size: var(--text-xs);
  color: var(--ink-mute);
  font-weight: 400;
  letter-spacing: 0.05em;
}
/* Lessons Grid & Cards */
.lessons-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.4rem;
}
@media(min-width: 768px) {
  .lessons-grid {
    grid-template-columns: 1fr 1fr;
  }
}
@media(min-width: 1200px) {
  .lessons-grid {
    grid-template-columns: 1fr 1fr 1fr;
  }
}
.lesson-card {
  background: var(--card);
  border: 1px solid var(--hair);
  border-radius: 6px;
  padding: 1.4rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  text-decoration: none;
  color: inherit;
  box-shadow: 0 3px 12px rgba(0, 0, 0, 0.015);
}
.lesson-card:hover {
  transform: translateY(-4px);
  border-color: var(--accent);
  box-shadow: 0 8px 24px var(--hair-soft);
}
.lesson-card-top {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}
.lesson-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.8rem;
}
.lesson-badge {
  font-family: var(--mono);
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--accent);
  border: 1px solid var(--accent);
  padding: 0.15rem 0.5rem;
  border-radius: 3px;
  background: color-mix(in srgb, var(--accent) 6%, transparent);
}
.lesson-status-badge {
  font-family: var(--mono);
  font-size: var(--text-2xs);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.15rem 0.45rem;
  border-radius: 3px;
  font-weight: 600;
}
.lesson-status-badge.not-started {
  background: var(--paper-3);
  color: var(--ink-mute);
}
.lesson-status-badge.in-progress {
  background: color-mix(in srgb, var(--accent) 10%, transparent);
  color: var(--accent);
}
.lesson-status-badge.completed {
  background: color-mix(in srgb, var(--good) 10%, transparent);
  color: var(--good);
}
.lesson-card h3 {
  font-size: var(--text-md);
  font-weight: 800;
  line-height: 1.25;
  color: var(--ink);
}
.lesson-pes {
  font-family: var(--mono);
  font-size: var(--text-2xs);
  color: var(--ink-mute);
  letter-spacing: 0.05em;
}
.lesson-desc {
  font-family: var(--serif);
  font-size: var(--text-base);
  line-height: 1.45;
  color: var(--ink-soft);
  margin-top: 0.4rem;
}
.lesson-card-bottom {
  margin-top: 1.4rem;
  padding-top: 0.8rem;
  border-top: 1px solid var(--hair-soft);
}
.lesson-progress-container {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}
.lesson-progress-meta {
  display: flex;
  justify-content: space-between;
  font-family: var(--mono);
  font-size: var(--text-2xs);
  color: var(--ink-mute);
  letter-spacing: 0.05em;
}
.lesson-progress-bar-bg {
  width: 100%;
  height: 5px;
  background: var(--paper-3);
  border-radius: 3px;
  overflow: hidden;
}
.lesson-progress-bar {
  height: 100%;
  background: var(--accent);
  width: 0%;
  transition: width 0.4s ease;
  border-radius: 3px;
}
.lesson-progress-bar.completed {
  background: var(--good);
}
/* No results state */
.no-results {
  text-align: center;
  padding: 3rem 0;
  font-family: var(--serif);
  font-style: italic;
  color: var(--ink-mute);
  font-size: var(--text-md);
}
/* ---- Glossary Panel ---- */
.glossary-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
  margin-top: 2rem;
}
@media(min-width: 768px) {
  .glossary-grid {
    grid-template-columns: 1fr 1fr;
  }
}
.glossary-card {
  background: var(--card);
  border: 1px solid var(--hair-soft);
  border-radius: 6px;
  padding: 1.2rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  gap: 0.6rem;
  transition: all 0.2s ease;
}
.glossary-card:hover {
  border-color: var(--accent-soft);
}
.glossary-card-top {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}
.glossary-term {
  font-family: var(--display);
  font-size: var(--text-md);
  font-weight: 800;
  color: var(--accent);
  letter-spacing: -0.01em;
}
.glossary-definition {
  font-family: var(--serif);
  font-size: var(--text-base);
  line-height: 1.5;
  color: var(--ink-soft);
}
.glossary-link {
  align-self: flex-start;
  font-family: var(--mono);
  font-size: var(--text-2xs);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-mute);
  text-decoration: none;
  border-bottom: 1px dashed var(--hair);
  padding-bottom: 1px;
  transition: all 0.15s ease;
}
.glossary-link:hover {
  color: var(--accent);
  border-color: var(--accent-soft);
}
/* ---- Resources Panel ---- */
.resources-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2.2rem;
  margin-top: 2rem;
}
@media(min-width: 992px) {
  .resources-grid {
    grid-template-columns: 1fr 1fr;
  }
}
.resource-group {
  background: var(--card);
  border: 1px solid var(--hair);
  border-radius: 6px;
  padding: 1.6rem;
}
.resource-group h3 {
  font-size: var(--text-lg);
  font-weight: 800;
  color: var(--ink);
  margin-bottom: 1.2rem;
  border-bottom: 2px solid var(--accent-soft);
  padding-bottom: 0.3rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.resource-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.resource-category-title {
  font-family: var(--mono);
  font-size: var(--text-2xs);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-mute);
  margin-top: 0.4rem;
  margin-bottom: 0.2rem;
  border-left: 2px solid var(--hair);
  padding-left: 0.4rem;
}
.resource-item {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  padding: 0.6rem 0.8rem;
  background: var(--paper-2);
  border: 1px solid var(--hair-soft);
  border-radius: 4px;
  text-decoration: none;
  color: var(--ink-soft);
  transition: all 0.18s ease;
}
.resource-item:hover {
  background: var(--paper-3);
  border-color: var(--accent-soft);
  color: var(--accent);
  transform: translateX(3px);
}
.resource-icon {
  flex-shrink: 0;
  width: 18px;
  height: 18px;
  color: var(--ink-mute);
}
.resource-item:hover .resource-icon {
  color: var(--accent);
}
.resource-title {
  font-family: var(--display);
  font-size: var(--text-base);
  font-weight: 600;
  line-height: 1.35;
}
/* PE Resources Section */
.pe-resource-section {
  background: var(--card);
  border: 1px solid var(--hair);
  border-radius: 6px;
  padding: 1.5rem;
  margin-bottom: 1.75rem;
}
.pe-resource-header {
  margin-bottom: 1.25rem;
  border-bottom: 1px solid var(--hair-soft);
  padding-bottom: 0.85rem;
}
.pe-resource-title {
  font-size: var(--text-md);
  font-weight: 800;
  color: var(--ink);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  flex-wrap: wrap;
}
.pe-resource-count {
  font-family: var(--mono);
  font-size: var(--text-xs);
  font-weight: normal;
  color: var(--ink-mute);
  background: var(--paper-2);
  padding: 0.2rem 0.55rem;
  border-radius: 999px;
  border: 1px solid var(--hair-soft);
}
.pe-resource-standard {
  font-family: var(--display);
  font-size: var(--text-sm);
  color: var(--ink-soft);
  margin: 0.4rem 0 0;
  font-style: italic;
  line-height: 1.45;
}
.pe-resource-subgrid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.25rem;
}
.pe-resource-column {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}
.pe-column-title {
  font-family: var(--mono);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-mute);
  padding-bottom: 0.25rem;
  border-bottom: 1px solid var(--hair-soft);
  margin-bottom: 0.2rem;
}
/* ============================================================
   PERIODIC TABLE DROPDOWN DRAWER - see docs/archive/TEXTBOOK_TODO.md, section 5
   ============================================================ */
.ptable-drawer-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(22, 32, 28, 0.4);
  z-index: 100;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease;
}
:root.dark .ptable-drawer-overlay {
  background: rgba(0, 0, 0, 0.6);
}
.ptable-drawer-overlay.open {
  opacity: 1;
  pointer-events: auto;
}
.ptable-drawer {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  width: 460px;
  max-width: 100vw;
  background-color: var(--paper);
  border-left: 1px solid var(--hair);
  z-index: 101;
  display: flex;
  flex-direction: column;
  box-shadow: -5px 0 25px rgba(0, 0, 0, 0.15);
  transform: translateX(100%);
  transition: transform 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}
.ptable-drawer.open {
  transform: translateX(0);
}
.ptable-drawer-header {
  padding: 1rem 1.25rem;
  border-bottom: 1px solid var(--hair);
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--paper-2);
}
.ptable-drawer-header h3 {
  font-size: var(--text-lg);
  margin: 0;
  font-family: var(--display);
}
.ptable-close-btn {
  background: none;
  border: none;
  font-size: var(--text-2xl);
  color: var(--ink-mute);
  cursor: pointer;
  line-height: 1;
  padding: 0;
  transition: color 0.2s;
}
.ptable-close-btn:hover {
  color: var(--accent);
}
.ptable-drawer-body {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  min-height: 0;
}
/* Control tabs for heatmaps */
.ptable-controls {
  padding: 1rem 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  border-bottom: 1px solid var(--hair-soft);
}
.ptable-tabs {
  display: flex;
  background: var(--paper-2);
  border-radius: 4px;
  padding: 2px;
  gap: 2px;
}
.ptable-tab {
  flex: 1;
  border: none;
  background: none;
  font-family: var(--mono);
  font-size: var(--text-2xs);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-mute);
  padding: 0.4rem 0.2rem;
  cursor: pointer;
  border-radius: 3px;
  transition: all 0.2s;
  text-align: center;
}
.ptable-tab:hover {
  color: var(--ink);
}
.ptable-tab.active {
  background: var(--card);
  color: var(--accent);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
}
/* Scrollable container for standard 18-col layout */
.ptable-grid-container {
  overflow-x: auto;
  padding: 1.25rem;
  border-bottom: 1px solid var(--hair-soft);
}
.ptable-grid {
  display: grid;
  grid-template-columns: repeat(18, 1fr);
  grid-template-rows: repeat(4, 1fr);
  gap: 4px;
  min-width: 680px; /* Force standard proportions on narrow drawer */
}
/* Cells styling */
.ptable-cell {
  position: relative;
  aspect-ratio: 1;
  border: 1px solid var(--hair);
  border-radius: 4px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  user-select: none;
  transition: border-color 0.2s, transform 0.1s, box-shadow 0.2s, background-color 0.2s, color 0.2s;
  box-sizing: border-box;
}
.ptable-cell:hover {
  border-color: var(--accent);
  z-index: 5;
  transform: scale(1.08);
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.1);
}
.ptable-cell.selected {
  border-color: var(--accent) !important;
  border-width: 2px !important;
  z-index: 6;
  transform: scale(1.08);
  box-shadow: 0 0 0 2px var(--accent-soft);
}
.ptable-cell .cell-z {
  font-family: var(--mono);
  font-size: var(--text-3xs);
  color: var(--ink-mute);
  position: absolute;
  top: 1px;
  left: 2px;
  pointer-events: none;
}
.ptable-cell .cell-sym {
  font-family: var(--mono);
  font-size: var(--text-xs);
  font-weight: 700;
  line-height: 1.1;
  margin-top: 2px;
  pointer-events: none;
}
.ptable-cell .cell-val {
  font-family: var(--mono);
  font-size: var(--text-3xs);
  line-height: 1;
  margin-top: 1px;
  text-align: center;
  pointer-events: none;
}
/* Category styling (Default Kind view) */
.ptable-cell.kind-metal {
  background-color: var(--paper-3);
  color: var(--ink);
}
.ptable-cell.kind-metalloid {
  background-color: var(--paper-2);
  border-color: var(--ink-soft);
  color: var(--ink);
}
.ptable-cell.kind-nonmetal {
  background-color: var(--card);
  border-color: var(--ink-mute);
  color: var(--accent);
}
.ptable-cell.kind-noble {
  background-color: var(--card);
  opacity: 0.75;
  color: var(--ink-mute);
}
/* No data/null trend formatting */
.ptable-cell.no-data {
  background-image: repeating-linear-gradient(45deg, var(--hair-soft) 0, var(--hair-soft) 1px, transparent 0, transparent 4px);
  background-color: var(--card) !important;
  color: var(--ink-mute) !important;
  opacity: 0.55;
}
/* Legend inside body */
.ptable-legend {
  padding: 0 1.25rem 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  font-family: var(--mono);
  font-size: var(--text-3xs);
  color: var(--ink-mute);
}
.ptable-legend-gradient {
  flex: 1;
  max-width: 180px;
  height: 8px;
  border-radius: 4px;
  border: 1px solid var(--hair-soft);
}
.ptable-legend-swatches {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 0.75rem;
  justify-content: center;
}
.ptable-legend-swatch {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}
.ptable-legend-chip {
  width: 10px;
  height: 10px;
  border-radius: 2px;
  border: 1px solid var(--hair-soft);
}
/* Detail Panel Styling */
.ptable-detail-panel {
  padding: 1.25rem;
  background-color: var(--paper-2);
  border-top: 1px solid var(--hair);
  min-height: 180px;
  display: flex;
  flex-direction: column;
}
.ptable-detail-placeholder {
  color: var(--ink-mute);
  font-size: var(--text-sm);
  text-align: center;
  margin: auto;
  line-height: 1.5;
}
.ptable-detail-content {
  display: flex;
  gap: 1.25rem;
  width: 100%;
}
.ptable-detail-main {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}
.ptable-detail-atom-header {
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
}
.ptable-detail-sym {
  font-family: var(--mono);
  font-size: var(--text-3xl);
  font-weight: 700;
  line-height: 1;
  color: var(--accent);
}
.ptable-detail-z {
  font-family: var(--mono);
  font-size: var(--text-sm);
  color: var(--ink-mute);
}
.ptable-detail-name {
  font-family: var(--display);
  font-size: var(--text-base);
  font-weight: 700;
  color: var(--ink);
  line-height: 1.2;
}
.ptable-detail-kind-tag {
  align-self: flex-start;
  font-family: var(--mono);
  font-size: var(--text-3xs);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 1px 6px;
  border-radius: 3px;
  background: var(--card);
  border: 1px solid var(--hair);
  color: var(--ink-soft);
  margin-top: 0.15rem;
}
.ptable-detail-stats {
  margin-top: 0.5rem;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  font-family: var(--mono);
  font-size: var(--text-2xs);
}
.ptable-detail-stat-row {
  display: flex;
  justify-content: space-between;
  border-bottom: 1px dashed var(--hair-soft);
  padding-bottom: 2px;
}
.ptable-detail-stat-label {
  color: var(--ink-mute);
}
.ptable-detail-stat-val {
  font-weight: 600;
  color: var(--ink);
}
.ptable-detail-visual {
  width: 140px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}
.ptable-bohr-svg {
  width: 120px;
  height: 120px;
  display: block;
}
.ptable-bohr-cap {
  font-family: var(--mono);
  font-size: var(--text-3xs);
  color: var(--ink-mute);
  margin-top: 0.25rem;
  text-align: center;
}
@media (max-width: 480px) {
  .ptable-drawer {
    width: 100vw;
  }
}
.ptable-control-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.25rem;
}
.ptable-toggle-label {
  font-family: var(--mono);
  font-size: var(--text-3xs);
  color: var(--ink-soft);
  display: flex;
  align-items: center;
  gap: 0.35rem;
  cursor: pointer;
  user-select: none;
}
.ptable-toggle-label input {
  cursor: pointer;
  accent-color: var(--accent);
}
/* Reference Tray Tabs */
.ptable-drawer-tabs {
  display: flex;
  background: var(--paper-3);
  padding: 4px;
  gap: 4px;
  border-bottom: 1px solid var(--hair);
}
.ptable-drawer-tab {
  flex: 1;
  border: none;
  background: none;
  font-family: var(--display);
  font-size: var(--text-2xs);
  font-weight: 700;
  text-transform: uppercase;
  color: var(--ink-mute);
  padding: 0.5rem 0.2rem;
  cursor: pointer;
  border-radius: 3px;
  transition: all 0.2s;
  text-align: center;
}
.ptable-drawer-tab:hover {
  color: var(--ink);
  background: var(--paper-2);
}
.ptable-drawer-tab.active {
  background: var(--card);
  color: var(--accent);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}
.ptable-panel {
  display: none;
  flex: 1;
  flex-direction: column;
  min-height: 0;
}
.ptable-panel.active {
  display: flex;
}
/* Formulas & Tables Panel styling */
.ptable-formulas-container {
  padding: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}
.ptable-ref-section {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.ptable-ref-section h4 {
  font-family: var(--display);
  font-size: var(--text-sm);
  color: var(--accent);
  border-bottom: 1px solid var(--hair-soft);
  padding-bottom: 4px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 700;
}
.ptable-ref-section p {
  font-size: var(--text-xs);
  line-height: 1.5;
  color: var(--ink-soft);
}
.ptable-bridge-diagram {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--paper-2);
  padding: 0.75rem 0.5rem;
  border-radius: 4px;
  font-family: var(--mono);
  font-size: var(--text-3xs);
  margin-top: 0.25rem;
  text-align: center;
  border: 1px solid var(--hair-soft);
}
.ptable-bridge-node {
  background: var(--card);
  padding: 4px 8px;
  border-radius: 3px;
  border: 1px solid var(--hair);
  font-weight: 600;
  color: var(--ink);
}
.ptable-bridge-arrow {
  color: var(--ink-mute);
  display: flex;
  flex-direction: column;
  font-size: var(--text-3xs);
  line-height: 1.2;
}
/* Reference table styling */
.ptable-ref-table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--mono);
  font-size: var(--text-2xs);
  margin-top: 0.25rem;
}
.ptable-ref-table th, .ptable-ref-table td {
  padding: 6px 8px;
  text-align: left;
  border-bottom: 1px solid var(--hair-soft);
}
.ptable-ref-table th {
  background: var(--paper-2);
  color: var(--ink-soft);
  font-weight: 600;
}
.ptable-ref-table tr:hover td {
  background: var(--paper-2);
}
/* Calculator Panel styling */
.ptable-calc-container {
  padding: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.ptable-calc-display-wrap {
  background: var(--card);
  border: 1px solid var(--hair);
  border-radius: 6px;
  padding: 0.75rem;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  min-height: 70px;
  justify-content: center;
}
.ptable-calc-expr {
  font-family: var(--mono);
  font-size: var(--text-2xs);
  color: var(--ink-mute);
  min-height: 1rem;
  word-break: break-all;
  text-align: right;
  width: 100%;
}
.ptable-calc-result {
  font-family: var(--mono);
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--ink);
  margin-top: 4px;
  word-break: break-all;
  text-align: right;
  width: 100%;
}
.ptable-calc-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
}
.ptable-calc-btn {
  border: 1px solid var(--hair);
  background: var(--card);
  font-family: var(--mono);
  font-size: var(--text-base);
  font-weight: 600;
  color: var(--ink);
  height: 42px;
  border-radius: 4px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.15s;
}
.ptable-calc-btn:hover {
  background: var(--paper-2);
  border-color: var(--ink-soft);
}
.ptable-calc-btn:active {
  transform: scale(0.95);
}
.ptable-calc-btn.op {
  background: var(--paper-2);
  color: var(--accent);
}
.ptable-calc-btn.action {
  background: var(--paper-3);
  color: var(--ink);
}
.ptable-calc-btn.equals {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.ptable-calc-btn.equals:hover {
  background: var(--accent-soft);
}
/* Calculator Helper Tool styling */
.ptable-calc-helper {
  background: var(--paper-2);
  border: 1px solid var(--hair-soft);
  border-radius: 6px;
  padding: 0.75rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin-top: 0.5rem;
}
.ptable-calc-helper-title {
  font-family: var(--display);
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--ink-soft);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 2px;
}
.ptable-calc-helper-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.ptable-calc-helper-field {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.ptable-calc-helper-field span {
  font-family: var(--mono);
  font-size: var(--text-3xs);
  color: var(--ink-mute);
}
.ptable-calc-helper-field input {
  border: 1px solid var(--hair);
  background: var(--card);
  font-family: var(--mono);
  font-size: var(--text-xs);
  padding: 4px 6px;
  border-radius: 3px;
  color: var(--ink);
  width: 100%;
}
.ptable-calc-helper-field input:focus {
  border-color: var(--accent);
  outline: none;
}
.ptable-calc-helper-arrow {
  font-family: var(--mono);
  font-size: var(--text-sm);
  color: var(--ink-mute);
  margin-top: 10px;
}
/* Exclude narrative prose when Quick Check is active */
body.quick-check-active p:not(.w-prompt):not(.w-feedback):not(.w-opt):not(.w-progress-hint):not(.d-cap):not(.diagram-cap):not(.lede):not(.w-construct-label):not(.w-construct-val),
body.quick-check-active ul:not(.w-sort-bins):not(.w-construct-pool):not(.toc-drop ul):not(.synopsis-claims ul):not(.synopsis-checklist ul),
body.quick-check-active ol,
body.quick-check-active blockquote,
body.quick-check-active .meta-strip,
body.quick-check-active h2:not(.w-prompt h2):not(.w-prompt > h2):not(.widget-section h2):not(.w-sort-card h2) {
  display: none !important;
}
/* --- Practice Review Grading Buttons --- */
.btn-forgot {
  background: var(--bad, #e06c75);
  color: #fff !important;
  border-color: var(--bad, #e06c75) !important;
}
.btn-forgot:hover {
  background: color-mix(in srgb, var(--bad, #e06c75) 80%, black) !important;
  border-color: color-mix(in srgb, var(--bad, #e06c75) 80%, black) !important;
}
.btn-hard {
  background: var(--warn, #d19a66);
  color: #fff !important;
  border-color: var(--warn, #d19a66) !important;
}
.btn-hard:hover {
  background: color-mix(in srgb, var(--warn, #d19a66) 80%, black) !important;
  border-color: color-mix(in srgb, var(--warn, #d19a66) 80%, black) !important;
}
.btn-easy {
  background: var(--good, #98c379);
  color: #fff !important;
  border-color: var(--good, #98c379) !important;
}
.btn-easy:hover {
  background: color-mix(in srgb, var(--good, #98c379) 80%, black) !important;
  border-color: color-mix(in srgb, var(--good, #98c379) 80%, black) !important;
}
/* ============================================================
   SOCRATIC COMPANION MASCOT WIDGET
   Floating buddy button + drawer for inquiry-based coaching
   ============================================================ */
.chem-socratic-widget {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 55;
  font-family: var(--display, system-ui, sans-serif);
}
.chem-mascot-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px 8px 8px;
  background: color-mix(in srgb, var(--card) 92%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--hair);
  border-radius: 9999px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
  cursor: pointer;
  transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  color: var(--ink);
}
.chem-mascot-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.18);
  border-color: var(--accent);
}
.chem-mascot-avatar {
  position: relative;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: color-mix(in srgb, var(--accent) 15%, transparent);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent);
  flex-shrink: 0;
}
.chem-mascot-btn--locked {
  border-style: dashed;
  border-color: var(--hair, var(--hair));
}
.chem-mascot-lock-badge {
  position: absolute;
  bottom: -2px;
  right: -2px;
  width: 14px;
  height: 14px;
  background: var(--card);
  border: 1px solid var(--hair);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-3xs);
  line-height: 1;
}
.chem-mascot-pill-tag {
  display: inline-flex;
  align-items: center;
  margin-left: 5px;
  padding: 1px 6px;
  background: color-mix(in srgb, var(--accent) 15%, transparent);
  color: var(--accent);
  border-radius: 4px;
  font-size: var(--text-2xs);
  letter-spacing: 0.04em;
  font-weight: 700;
  text-transform: uppercase;
}
.chem-mascot-svg {
  width: 26px;
  height: 26px;
}
.chem-mascot-pill {
  font-family: var(--mono, monospace);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink);
}
/* Socratic Drawer */
.chem-socratic-drawer {
  position: fixed;
  bottom: 84px;
  right: 24px;
  width: 380px;
  max-width: calc(100vw - 32px);
  height: 520px;
  max-height: calc(100vh - 120px);
  background: var(--card);
  border: 1px solid var(--hair);
  border-radius: 20px;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.2);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px) scale(0.96);
  transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  z-index: 56;
}
.chem-socratic-drawer.open {
  opacity: 1;
  visibility: visible;
  transform: translateY(0) scale(1);
}
.chem-socratic-head {
  padding: 14px 18px;
  border-bottom: 1px solid var(--hair-soft);
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: color-mix(in srgb, var(--paper-2) 60%, var(--card));
}
.chem-socratic-title-group {
  display: flex;
  align-items: center;
  gap: 10px;
}
.chem-socratic-badge-icon {
  font-size: var(--text-xl);
  line-height: 1;
}
.chem-socratic-title {
  margin: 0;
  font-size: var(--text-base);
  font-weight: 800;
  color: var(--ink);
  letter-spacing: -0.01em;
}
.chem-socratic-subtitle {
  display: block;
  font-size: var(--text-xs);
  color: var(--ink-mute);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 230px;
}
.chem-socratic-close-btn {
  background: transparent;
  border: none;
  font-size: var(--text-xl);
  line-height: 1;
  color: var(--ink-mute);
  cursor: pointer;
  padding: 4px;
  border-radius: 6px;
  transition: color 0.15s;
}
.chem-socratic-close-btn:hover {
  color: var(--accent);
}
.chem-socratic-body {
  padding: 16px;
  display: flex;
  flex-direction: column;
  flex: 1;
  min-height: 0;
  gap: 12px;
  overflow-y: auto;
}
/* Unauthenticated Tip & Lock Card */
.chem-socratic-tip-card {
  padding: 14px;
  border-radius: 14px;
  background: color-mix(in srgb, var(--accent) 8%, var(--card));
  border: 1px solid color-mix(in srgb, var(--accent) 25%, transparent);
}
.chem-socratic-tip-badge {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: var(--text-sm);
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 6px;
}
.chem-socratic-tip-text {
  margin: 0;
  font-size: var(--text-sm);
  line-height: 1.45;
  color: var(--ink-soft);
}
.chem-socratic-lock-card {
  margin-top: auto;
  padding: 18px;
  border-radius: 14px;
  background: var(--paper-2);
  border: 1px solid var(--hair);
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}
.chem-lock-icon {
  font-size: var(--text-2xl);
  line-height: 1;
}
.chem-lock-title {
  margin: 0;
  font-size: var(--text-base);
  font-weight: 800;
  color: var(--ink);
}
.chem-lock-desc {
  margin: 0;
  font-size: var(--text-sm);
  line-height: 1.45;
  color: var(--ink-mute);
}
.chem-lock-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 100%;
  padding: 10px 14px;
  margin-top: 4px;
  border-radius: 10px;
  background: var(--accent);
  color: var(--card);
  font-size: var(--text-sm);
  font-weight: 700;
  text-decoration: none;
  transition: opacity 0.2s;
}
.chem-lock-btn:hover {
  opacity: 0.9;
}
.chem-lock-note {
  font-size: var(--text-xs);
  color: var(--ink-mute);
  line-height: 1.35;
}
/* Authenticated Chat UI */
.chem-chat-history {
  flex: 1;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding-right: 4px;
}
.chem-msg {
  max-width: 85%;
  padding: 10px 14px;
  font-size: var(--text-sm);
  line-height: 1.45;
  word-break: break-word;
}
.chem-msg p {
  margin: 0;
}
.chem-msg-bot {
  align-self: flex-start;
  background: var(--paper-2);
  border: 1px solid var(--hair-soft);
  color: var(--ink);
  border-radius: 14px 14px 14px 2px;
}
.chem-msg-user {
  align-self: flex-end;
  background: var(--accent);
  color: var(--card);
  border-radius: 14px 14px 2px 14px;
}
.chem-coach-dots {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 4px;
}
.chem-coach-dots span {
  width: 6px;
  height: 6px;
  background: var(--ink-mute);
  border-radius: 50%;
  animation: chem-dots 1.2s infinite ease-in-out;
}
.chem-coach-dots span:nth-child(2) { animation-delay: 0.2s; }
.chem-coach-dots span:nth-child(3) { animation-delay: 0.4s; }
@keyframes chem-dots {
  0%, 80%, 100% { transform: scale(0.6); opacity: 0.4; }
  40% { transform: scale(1); opacity: 1; }
}
.chem-chat-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}
.chem-chat-chip {
  background: var(--paper-2);
  border: 1px solid var(--hair);
  color: var(--ink-soft);
  font-size: var(--text-xs);
  padding: 5px 10px;
  border-radius: 999px;
  cursor: pointer;
  transition: all 0.15s;
  white-space: nowrap;
}
.chem-chat-chip:hover {
  border-color: var(--accent);
  color: var(--accent);
}
.chem-chat-form {
  display: flex;
  align-items: center;
  gap: 8px;
  padding-top: 4px;
}
.chem-chat-form input {
  flex: 1;
  background: var(--paper-2);
  border: 1px solid var(--hair);
  color: var(--ink);
  border-radius: 10px;
  padding: 9px 12px;
  font-size: var(--text-sm);
  outline: none;
  transition: border-color 0.2s;
}
.chem-chat-form input:focus {
  border-color: var(--accent);
}
.chem-chat-form button {
  width: 36px;
  height: 36px;
  background: var(--accent);
  color: var(--card);
  border: none;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: opacity 0.2s;
  flex-shrink: 0;
}
.chem-chat-form button:hover {
  opacity: 0.9;
}
@media (max-width: 600px) {
  .chem-socratic-widget {
    bottom: 16px;
    right: 16px;
  }
  .chem-socratic-drawer {
    bottom: 72px;
    right: 12px;
    left: 12px;
    width: auto;
    max-height: calc(100vh - 90px);
  }
}
@media print {
  .chem-socratic-widget {
    display: none !important;
  }
}

/* ---- Quick Check and Cram View: top-bar tools, set by book.js ---- */
.tb-btn[data-tool="quick-check"][aria-pressed="true"] { color: var(--paper); background: var(--good); border-color: var(--good); }
.tb-btn[data-tool="cram-view"][aria-pressed="true"] { color: var(--paper); background: var(--accent); border-color: var(--accent); }
.tb-btn[data-tool="clear-progress"]:hover { color: var(--bad); border-color: var(--bad); }

/* ---- print: what only chem adds to the shared print rules ---- */
@media print {
  .resume-bar, .textbook-bridge, .chem-socratic-widget { display: none !important; }
}

/* ---- the top bar on a phone ----
   Chem's bar carries up to eight 44px buttons (Home, Quick Check, Cram View, References,
   Feedback, Contents, Print, theme), which is wider than a 360px screen. Both groups flow as one
   wrapping row, so seven buttons fit the first line and the page never scrolls sideways. */
@media (max-width: 600px) {
  .topbar { flex-wrap: wrap; justify-content: flex-start; gap: 0.25rem; }
  .topbar-left, .topbar-right { display: contents; }
}

/* ---- cards and sim boxes on a phone ----
   Flex and grid items default to min-width: auto, so a row of controls inside a card or a sim box
   refuses to shrink and pushes the page sideways. Zero specificity, so any rule that sets a real
   min-width still wins. */
:where(.interactive) :where(div, section, label, form, span, input, select, button) { min-width: 0; }
:where(.sim-box) :where(div, section, label, form, span, input, select, button) { min-width: 0; }
:where(.interactive) :where(select, input[type="text"], textarea) { max-width: 100%; }
:where(.interactive) :where(svg, canvas) { max-width: 100%; }
:where(.sim-box) :where(select, input[type="text"], textarea) { max-width: 100%; }
:where(.sim-box) :where(svg, canvas) { max-width: 100%; }

/* the building tools sit in a .wrap section, which has no flow gap of its own */
.wrap > .sim-box { margin-top: var(--gap-block); }

/* with chem's tools the bar is full before the crumb has room; the crumb steps aside instead of squeezing Home */
.topbar-left { flex-shrink: 0; }
@media (max-width: 1180px) { .crumb { display: none; } }

/* ============================================================
   LESSON-ONLY LAYOUTS (moved from <style> blocks)
   ============================================================ */
/* ---- 1-2c: moved from the lesson's <style> block ---- */
  /* Custom interactive widget styles for Nomenclature */
  .nomen-tree-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
    margin-top: 1rem;
  }
  @media (max-width: 700px) {
    .nomen-tree-grid { grid-template-columns: 1fr; }
  }
  .nomen-branch-card {
    background: var(--card);
    border: 1px solid var(--hair);
    border-radius: 8px;
    padding: 1.25rem;
    box-shadow: 0 2px 8px rgba(0,0,0,.06);
    cursor: pointer;
    position: relative;
    transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
  }
  .nomen-branch-card:hover, .nomen-branch-card:focus-visible {
    transform: translateY(-2px);
    border-color: var(--accent);
    box-shadow: 0 6px 18px rgba(0,0,0,.1);
  }
  .nomen-branch-card.expanded {
    grid-column: 1 / -1;
    border-color: var(--accent);
    background: var(--paper-2);
    box-shadow: 0 8px 24px rgba(0,0,0,.15);
  }
  .nomen-branch-card.expanded p,
  .nomen-branch-card.expanded ul {
    font-size: var(--text-base) !important;
  }
  .branch-expand-cue {
    position: absolute;
    top: 0.8rem;
    right: 0.8rem;
    font-family: var(--mono);
    font-size: var(--text-2xs);
    background: var(--hair-soft);
    color: var(--ink-soft);
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
    pointer-events: none;
    transition: background 0.2s, color 0.2s;
  }
  .nomen-branch-card.expanded .branch-expand-cue {
    background: var(--accent);
    color: var(--paper);
  }
  .nomen-branch-card h4 {
    margin-top: 0;
    color: var(--accent);
    font-family: var(--display);
    font-size: var(--text-md);
  }
  .ion-flex-row {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
    margin: 1rem 0;
  }
  .ion-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.4rem 0.8rem;
    border-radius: 20px;
    font-family: var(--mono);
    font-weight: 600;
    font-size: var(--text-base);
  }
  .ion-pill.cation {
    background: color-mix(in srgb, var(--accent) 15%, var(--card));
    border: 1px solid var(--accent);
    color: var(--accent);
  }
  .ion-pill.anion {
    background: color-mix(in srgb, var(--cool) 15%, var(--card));
    border: 1px solid var(--cool);
    color: var(--cool);
  }
  .prefix-table-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
    gap: 0.75rem;
    margin: 1rem 0;
  }
  .prefix-chip {
    background: var(--card);
    border: 1px solid var(--hair);
    border-radius: 6px;
    padding: 0.6rem;
    text-align: center;
    font-family: var(--mono);
    font-size: var(--text-base);
  }
  .prefix-chip span.num {
    font-weight: 700;
    color: var(--accent);
    margin-right: 0.2rem;
  }

/* ============================================================
   1-1b: the trend explorer and the reactivity chain (DOM tools in a .sim-box)
   Cell colours are set by data-hue and data-level, never by a style write, so a
   theme change recolours the table by itself.
   ============================================================ */
button.pcell { font: inherit; padding: 0; appearance: none; }
button.pcell:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.pcell[data-hue="noble"], .pcell[data-hue="none"] { background: var(--card); }
.pcell[data-hue="seq"][data-level="0"] { background: color-mix(in srgb, var(--cool) 100%, var(--paper-2)); color: var(--card); }
.pcell[data-hue="seq"][data-level="1"] { background: color-mix(in srgb, var(--cool) 75%, var(--paper-2)); color: var(--card); }
.pcell[data-hue="seq"][data-level="2"] { background: color-mix(in srgb, var(--cool) 50%, var(--paper-2)); color: var(--ink); }
.pcell[data-hue="seq"][data-level="3"] { background: color-mix(in srgb, var(--cool) 25%, var(--paper-2)); color: var(--ink); }
.pcell[data-hue="seq"][data-level="4"] { background: var(--paper-2); color: var(--ink); }
.pcell[data-hue="seq"][data-level="5"] { background: color-mix(in srgb, var(--accent) 25%, var(--paper-2)); color: var(--ink); }
.pcell[data-hue="seq"][data-level="6"] { background: color-mix(in srgb, var(--accent) 50%, var(--paper-2)); color: var(--ink); }
.pcell[data-hue="seq"][data-level="7"] { background: color-mix(in srgb, var(--accent) 75%, var(--paper-2)); color: var(--card); }
.pcell[data-hue="seq"][data-level="8"] { background: color-mix(in srgb, var(--accent) 100%, var(--paper-2)); color: var(--card); }
.pcell[data-hue="metal"][data-level="0"] { background: color-mix(in srgb, var(--accent) 18%, var(--card)); color: var(--ink); }
.pcell[data-hue="metal"][data-level="1"] { background: color-mix(in srgb, var(--accent) 36%, var(--card)); color: var(--ink); }
.pcell[data-hue="metal"][data-level="2"] { background: color-mix(in srgb, var(--accent) 54%, var(--card)); color: var(--ink); }
.pcell[data-hue="metal"][data-level="3"] { background: color-mix(in srgb, var(--accent) 72%, var(--card)); color: var(--card); }
.pcell[data-hue="metal"][data-level="4"] { background: color-mix(in srgb, var(--accent) 90%, var(--card)); color: var(--card); }
.pcell[data-hue="nonmetal"][data-level="0"] { background: color-mix(in srgb, var(--cool) 18%, var(--card)); color: var(--ink); }
.pcell[data-hue="nonmetal"][data-level="1"] { background: color-mix(in srgb, var(--cool) 36%, var(--card)); color: var(--ink); }
.pcell[data-hue="nonmetal"][data-level="2"] { background: color-mix(in srgb, var(--cool) 54%, var(--card)); color: var(--ink); }
.pcell[data-hue="nonmetal"][data-level="3"] { background: color-mix(in srgb, var(--cool) 72%, var(--card)); color: var(--card); }
.pcell[data-hue="nonmetal"][data-level="4"] { background: color-mix(in srgb, var(--cool) 90%, var(--card)); color: var(--card); }
.legend .bar { background: linear-gradient(90deg, var(--cool), var(--paper-2), var(--accent)); }
.legend .sw { display: inline-block; width: 13px; height: 13px; border: 1px solid var(--hair); flex-shrink: 0; }
.legend .sw-metal { background: color-mix(in srgb, var(--accent) 85%, var(--card)); }
.legend .sw-nonmetal { background: color-mix(in srgb, var(--cool) 85%, var(--card)); }
.legend .sw-noble { background: var(--card); }
.sim-box[data-tool][data-locked="true"] .ptable-scroll { opacity: 0.4; pointer-events: none; }
.tool-field { display: flex; flex-direction: column; gap: 0.3rem; font-family: var(--display); }
.chain-steps { list-style: none; padding: 0; display: grid; gap: 0.6rem; }
.chain-step { display: flex; align-items: baseline; gap: 0.8rem; margin: 0; padding: 0.7rem 1rem; background: var(--card); border: 1px solid var(--hair); border-radius: var(--r-ctl); font-size: var(--text-read); }
.chain-badge { flex: 0 0 auto; padding: 0.15rem 0.5rem; background: var(--paper-2); border: 1px solid var(--hair); border-radius: var(--r-tag); font-family: var(--mono); font-size: var(--text-xs); font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase; }
.chain-guess { display: grid; gap: 0.6rem; padding: 1rem; background: var(--paper-2); border: 1px solid var(--hair); border-radius: var(--r-ctl); }

/* ---- shared by the Unit 1 DOM tools: molecule drawing text, ion counters, step panel ---- */
.mol-atom { font-family: var(--mono); font-weight: 700; font-size: var(--text-xl); }
.mol-label { font-family: var(--display); font-size: var(--text-xs); }
.tool-step { display: grid; gap: 0.9rem; }
.ion-col { display: flex; flex-direction: column; align-items: center; gap: 0.5rem; }
.ion-count { display: flex; align-items: center; gap: 0.5rem; }
.ion-count output { min-width: 2.2rem; text-align: center; font-family: var(--mono); font-size: var(--text-lg); font-weight: 700; }
.ion-plus { font-family: var(--display); font-size: var(--text-xl); font-weight: 700; color: var(--ink-mute); }

.step-cards { display: grid; gap: var(--gap-block); }
.lewis-bond-group, .lewis-atom-group { cursor: pointer; }
.lewis-bond-group:hover .lewis-bond-visual { stroke: var(--accent); opacity: 0.9; }
.lewis-atom-group:hover .lewis-atom-text { filter: drop-shadow(0 0 4px var(--accent-soft)); }
.lewis-bond-group:focus-visible, .lewis-atom-group:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.readout[data-match="true"] .readout-value { color: var(--good); }
.readout[data-match="false"] .readout-value { color: var(--accent); }

/* ============================================================
   DASHBOARD (index.html). Moved from its <style> block.
   ============================================================ */
    .search-icon { width: 16px; height: 16px; }


    /* Local dashboard styles */
    .dashboard-container {
      max-width: 78rem;
      margin: 0 auto;
      padding: 2rem var(--gutter) 6rem;
    }

    /* Concept Map Tab Styles */
    .concept-map-container {
      width: 100%;
      max-width: 1100px;
      margin: 0 auto;
      background: var(--card);
      border: 1px solid var(--hair);
      border-radius: 12px;
      padding: 1.5rem;
      box-shadow: 0 4px 12px rgba(0,0,0,0.03);
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 1.5rem;
    }
    
    .concept-map-title {
      font-family: var(--display);
      font-size: var(--text-lg);
      font-weight: 700;
      color: var(--ink);
      margin-bottom: 0.5rem;
      text-align: center;
    }

    .concept-map-legend {
      display: flex;
      justify-content: center;
      gap: 1.5rem;
      margin-bottom: 0.5rem;
      flex-wrap: wrap;
    }

    .legend-item {
      display: flex;
      align-items: center;
      gap: 0.5rem;
      font-family: var(--mono);
      font-size: var(--text-xs);
      font-weight: 500;
      color: var(--ink-soft);
      text-transform: uppercase;
      letter-spacing: 0.05em;
    }

    .legend-color {
      width: 12px;
      height: 12px;
      border-radius: 3px;
    }

    .legend-color.not-started {
      background: var(--paper-3);
      border: 1px solid var(--ink-mute);
    }

    .legend-color.in-progress {
      background: color-mix(in srgb, var(--accent) 15%, transparent);
      border: 1.5px solid var(--accent);
    }

    .legend-color.completed {
      background: color-mix(in srgb, var(--good) 15%, transparent);
      border: 1.5px solid var(--good);
    }

    .concept-map-svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }

    /* Node Styles */
    .concept-node {
      transition: transform 0.2s ease, opacity 0.3s ease;
      transform-box: fill-box;
      transform-origin: center;
    }

    .concept-node:hover {
      transform: scale(1.03);
    }

    .node-bg {
      fill: var(--paper-3);
      stroke: var(--ink-mute);
      stroke-width: 1px;
      transition: fill 0.3s ease, stroke 0.3s ease, stroke-width 0.3s ease;
    }

    .concept-node:hover .node-bg {
      stroke-width: 1.5px;
    }

    /* Badge Text (Lesson ID) */
    .node-badge-text {
      font-family: var(--mono);
      font-size: var(--text-3xs);
      font-weight: 600;
      fill: var(--ink-mute);
      transition: fill 0.3s ease;
      letter-spacing: 0.05em;
    }

    /* Title Text */
    .node-title-text {
      font-family: var(--display);
      font-size: var(--text-2xs);
      font-weight: 700;
      fill: var(--ink-soft);
      transition: fill 0.3s ease;
    }

    .concept-node:hover .node-title-text {
      fill: var(--ink);
    }

    /* Node States */
    .concept-node.state-not-started .node-bg {
      fill: var(--paper-2);
      stroke: var(--ink-mute);
    }

    .concept-node.state-in-progress .node-bg {
      fill: color-mix(in srgb, var(--accent) 8%, var(--paper));
      stroke: var(--accent);
      stroke-width: 1.5px;
    }
    .concept-node.state-in-progress .node-badge-text {
      fill: var(--accent);
    }

    .concept-node.state-completed .node-bg {
      fill: color-mix(in srgb, var(--good) 8%, var(--paper));
      stroke: var(--good);
      stroke-width: 1.5px;
    }
    .concept-node.state-completed .node-badge-text {
      fill: var(--good);
    }

    /* Connection Arrows */
    #panel-concept-map .d-arrow {
      stroke: var(--ink-mute);
      stroke-width: 1.2px;
      stroke-dasharray: none;
      transition: stroke 0.3s ease, stroke-width 0.3s ease, opacity 0.3s ease;
    }

    #panel-concept-map .d-arrow.state-completed {
      stroke: var(--good);
      stroke-width: 1.6px;
    }

    #panel-concept-map .d-arrow.state-in-progress {
      stroke: var(--accent);
      stroke-dasharray: 4 2;
      stroke-width: 1.4px;
    }

    /* Responsive adjustment */
    @media (max-width: 600px) {
      .concept-map-container {
        padding: 0.75rem;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        align-items: flex-start;
      }
      .concept-map-title, .concept-map-legend {
        align-self: center;
      }
      .concept-map-svg {
        min-width: 680px; /* Keep nodes legible on mobile by scrolling instead of extreme shrinking */
      }
    }

    /* Cram Mode Styles */
    .cram-spinner-container {
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 3rem 0;
      gap: 1rem;
    }
    .cram-spinner {
      border: 4px solid var(--hair-soft);
      border-top: 4px solid var(--accent);
      border-radius: 50%;
      width: 40px;
      height: 40px;
      animation: spin 1s linear infinite;
    }
    @keyframes spin {
      0% { transform: rotate(0deg); }
      100% { transform: rotate(360deg); }
    }
    .cram-lesson-group {
      border: 1px solid var(--hair);
      background: var(--card);
      border-radius: 12px;
      padding: clamp(1.2rem, 3vw, 2rem);
      box-shadow: 0 4px 12px rgba(0,0,0,0.02);
    }
    .cram-lesson-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      border-bottom: 1px solid var(--hair-soft);
      padding-bottom: 0.75rem;
      margin-bottom: 1.5rem;
    }
    .cram-lesson-title {
      font-family: var(--display);
      font-size: var(--text-md);
      font-weight: 700;
      color: var(--ink);
    }
    .cram-lesson-badge {
      font-family: var(--mono);
      font-size: var(--text-xs);
      font-weight: 600;
      background: var(--paper-3);
      border: 1px solid var(--hair);
      padding: 0.2rem 0.5rem;
      border-radius: 4px;
      color: var(--ink-soft);
    }

    /* Force visibility and reset nested frames in Cram Mode & Practice Review */
    #panel-cram-mode .exam-frame,
    #panel-cram-mode .reveal,
    #panel-cram-mode .callout,
    #panel-practice-review .exam-frame,
    #panel-practice-review .reveal,
    #panel-practice-review .callout {
      opacity: 1 !important;
      transform: none !important;
      visibility: visible !important;
    }
    #panel-cram-mode .exam-frame {
      border: none !important;
      padding: 0 !important;
      margin: 0 !important;
      background: transparent !important;
      box-shadow: none !important;
    }
    #panel-cram-mode .textbox {
      max-width: 100% !important;
    }

    /* Practice & Review Layout */
    .practice-dashboard-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 2rem;
      align-items: start;
    }
    @media (max-width: 900px) {
      .practice-dashboard-grid {
        grid-template-columns: 1fr;
      }
    }
    .practice-main-card {
      border: 1px solid var(--hair);
      background: var(--card);
      border-radius: 12px;
      padding: 1.5rem;
      box-shadow: 0 4px 12px rgba(0,0,0,0.02);
      display: flex;
      flex-direction: column;
      gap: 1.25rem;
    }
    .practice-card-header {
      display: flex;
      align-items: center;
      gap: 0.75rem;
      border-bottom: 1px solid var(--hair-soft);
      padding-bottom: 0.75rem;
    }
    .practice-card-header h3 {
      font-family: var(--display);
      font-size: var(--text-md);
      font-weight: 700;
      color: var(--ink);
      margin: 0;
      flex-grow: 1;
    }
    .practice-icon {
      color: var(--accent);
    }
    .practice-badge {
      font-family: var(--mono);
      font-size: var(--text-xs);
      font-weight: 600;
      background: var(--accent);
      color: #fff;
      padding: 0.15rem 0.5rem;
      border-radius: 99px;
      border: none;
    }
    .practice-badge.zero {
      background: var(--paper-3);
      color: var(--ink-mute);
      border: 1px solid var(--hair);
    }
    .practice-card-content {
      min-height: 220px;
      display: flex;
      flex-direction: column;
      justify-content: flex-start;
    }
    .practice-placeholder-text {
      font-family: var(--serif);
      font-size: var(--text-sm);
      color: var(--ink-soft);
      text-align: center;
      line-height: 1.5;
      padding: 2.5rem 1rem;
      align-self: center;
    }
    
    /* Interactive Review Session CSS */
    .review-session-card {
      display: flex;
      flex-direction: column;
      gap: 1.25rem;
      text-align: left;
    }
    .review-meta {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-family: var(--mono);
      font-size: var(--text-xs);
      color: var(--ink-mute);
    }
    .review-prompt-container {
      border-left: 3px solid var(--accent);
      padding-left: 1rem;
      font-size: var(--text-base);
      color: var(--ink);
      line-height: 1.6;
    }
    .review-prompt-container input.blank {
      width: 100px;
      padding: 0.15rem 0.4rem;
      border: 1px solid var(--hair);
      border-radius: 4px;
      font-family: var(--mono);
      font-size: var(--text-sm);
      background: var(--paper-2);
      color: var(--ink);
      text-align: center;
    }
    .review-prompt-container .exam-meta {
      display: none; /* Hide internal metadata inside exam frame */
    }
    .review-prompt-container textarea {
      width: 100%;
      min-height: 80px;
      margin-top: 0.5rem;
      border-radius: 6px;
      border: 1px solid var(--hair);
      background: var(--paper-2);
      color: var(--ink);
      padding: 0.5rem;
      font-family: var(--serif);
    }
    .review-action-area {
      display: flex;
      flex-direction: column;
      gap: 0.75rem;
      margin-top: 0.5rem;
    }
    .review-grading-buttons {
      display: grid;
      grid-template-columns: 1fr 1fr 1fr;
      gap: 0.5rem;
    }
    
    .review-answer-display {
      background: var(--paper-2);
      border: 1px solid var(--hair);
      border-radius: 8px;
      padding: 1rem;
      font-size: var(--text-sm);
      line-height: 1.5;
      color: var(--ink-soft);
    }
    .review-answer-display strong.term {
      color: var(--accent);
      font-weight: 700;
    }
  
/* dashboard: legacy layout from inline styles */
.xdash-01 { font-family: var(--display); font-size: var(--text-sm); color: var(--ink-soft); margin: -0.4rem 0 1.2rem; font-style: italic; }
.xdash-02 { display: none; }
.xdash-03 { background: var(--card); border: 1.5px solid var(--accent); border-radius: 10px; padding: 1.25rem; margin-bottom: 1.25rem; display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 1rem; box-shadow: 0 3px 12px rgba(0,0,0,0.05); }
.xdash-04 { flex: 1; min-width: 16rem; }
.xdash-05 { display: flex; align-items: center; gap: 0.5rem; margin-bottom: 0.25rem; }
.xdash-06 { font-size: var(--text-2xs); }
.xdash-07 { font-family: var(--mono); font-size: var(--text-xs); color: var(--ink-mute); }
.xdash-08 { font-size: var(--text-base); font-weight: 700; margin: 0 0 0.25rem 0; }
.xdash-09 { font-size: var(--text-xs); color: var(--ink-soft); margin: 0; line-height: 1.4; }
.xdash-10 { text-decoration: none; white-space: nowrap; font-weight: 700; background: var(--accent); color: var(--paper-1,#fff); }
.xdash-11 { background: var(--card); border: 1.5px solid var(--accent); border-radius: 8px; padding: 1rem 1.25rem; margin-bottom: 1.25rem; display: flex; align-items: center; justify-content: space-between; gap: 1rem; flex-wrap: wrap; }
.xdash-12 { margin: 0; font-size: var(--text-2xs); }
.xdash-13 { margin-bottom: 1.5rem; background: var(--paper-2); border: 1px solid var(--hair-soft); }
.xdash-14 { font-size: var(--text-sm); color: var(--ink-soft); margin-top: 0.4rem; line-height: 1.45; }
.xdash-15 { color: var(--ink); }
.xdash-16 { color: var(--accent); text-decoration: underline; }
.xdash-17 { font-family: var(--mono); font-size: var(--text-sm); color: var(--ink-soft); }
.xdash-18 { display: none; flex-direction: column; gap: 2rem; }
.xdash-19 { width: 20px; height: 20px; }
.xdash-20 { padding: 0.25rem 0.5rem; font-size: var(--text-sm); }
.xdash-21 { padding: 0.25rem 0.5rem; font-size: var(--text-sm); text-decoration: none; }
.xdash-22 { font-size: var(--text-sm); color: var(--ink-soft); margin-bottom: 0.75rem; }
.xdash-23 { display: flex; gap: 0.5rem; flex-wrap: wrap; }
.xdash-24 { text-decoration: none; padding: 0.3rem 0.6rem; font-size: var(--text-xs); }
.xdash-25 { border: 1.5px solid var(--accent); background: var(--card); }
.xdash-26 { padding: 0.25rem 0.5rem; font-size: var(--text-sm); text-decoration: none; background: var(--accent); color: var(--paper-1, #fff); font-weight: 700; }
.xdash-27 { text-decoration: none; padding: 0.3rem 0.6rem; font-size: var(--text-xs); opacity: 0.85; }

/* ============================================================
   COLOPHON (about.html). Moved from its <style> block.
   ============================================================ */

  /* Colophon-only layout. Nothing here is used by a lesson page. */
  .colophon section { padding-top: var(--gap-section); padding-bottom: var(--gap-section); }
  .colophon .hero { min-height: auto; padding-top: 7rem; padding-bottom: var(--gap-section); }
  .colophon .hero h1 { max-width: 20ch; }

  .stack > * + * { margin-top: 1.1rem; }

  /* Two-column "who did what" split */
  .split {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
    margin: 2rem 0 0;
  }
  @media (min-width: 800px) { .split { grid-template-columns: 1fr 1fr; gap: 2.5rem; } }
  .split-col { border-top: 2px solid var(--ink); padding-top: .8rem; }
  .split-col h3 { font-size: var(--text-md); margin-bottom: .7rem; }
  .split-col ul { margin: 0; padding-left: 1.15rem; }
  .split-col li { font-family: var(--serif); font-size: var(--text-base); line-height: 1.5; color: var(--ink-soft); margin-bottom: .5rem; }

  /* Constraint list */
  .rules { list-style: none; margin: 1.8rem 0 0; padding: 0; }
  .rules li {
    border-left: 2px solid var(--hair);
    padding: .15rem 0 .15rem 1.1rem;
    margin-bottom: 1.15rem;
    font-family: var(--serif);
    font-size: var(--text-base);
    line-height: 1.5;
    color: var(--ink-soft);
    max-width: var(--prose);
  }
  .rules li b {
    display: block;
    font-family: var(--display);
    font-weight: 700;
    font-size: var(--text-base);
    color: var(--ink);
    margin-bottom: .2rem;
  }

  /* Version history */
  .history { margin-top: 2rem; max-width: var(--prose); }
  .rel { border-top: 1px solid var(--hair); padding: 1.15rem 0; }
  .rel:last-child { border-bottom: 1px solid var(--hair); }
  .rel-date {
    font-family: var(--mono);
    font-size: var(--text-xs);
    letter-spacing: .13em;
    text-transform: uppercase;
    color: var(--accent);
    margin-bottom: .35rem;
  }
  .rel-title {
    font-family: var(--display);
    font-weight: 700;
    font-size: var(--text-md);
    color: var(--ink);
    margin-bottom: .3rem;
    line-height: 1.25;
  }
  .rel p { font-family: var(--serif); font-size: var(--text-base); line-height: 1.5; color: var(--ink-soft); max-width: none; }

  .backlink {
    display: inline-block;
    font-family: var(--mono);
    font-size: var(--text-xs);
    letter-spacing: .12em;
    text-transform: uppercase;
    color: var(--ink-mute);
    text-decoration: none;
    border-bottom: 1px solid var(--hair);
    padding-bottom: .15rem;
  }
  .backlink:hover { color: var(--accent); border-color: var(--accent); }

  .colophon a { color: var(--accent); }

.xabout-01 { margin-top: 2rem; font-size: var(--text-base); }

/* ---- 1-2d to 2-6a, content pass (4c stage 3): named replacements for the old per-lesson classes ---- */
/* the Before-Change-After table in 2-7c: the three row kinds */
.bca-table tr.row-pending { font-weight: 700; }
.bca-table tr.row-change { color: var(--accent); }
.bca-table tr.row-change td.row-label { color: var(--accent); }
.bca-table tr.row-after { font-weight: 700; border-top: 1.8px solid var(--hair); }
/* the five-part argument cards in 2-6a */
.arg-steps { list-style: none; padding: 0; display: grid; gap: 0.75rem; margin: 1.5rem 0; }
.arg-step { padding: 1rem 1.2rem; border-left: 3px solid var(--accent); background: var(--card); }
.arg-step h4 { display: flex; align-items: center; gap: 0.6rem; margin: 0 0 0.35rem; }
.arg-step p { margin: 0; }
.arg-num { display: inline-flex; align-items: center; justify-content: center; width: 24px; height: 24px; border-radius: 50%; background: var(--accent-soft); color: var(--accent); font-weight: 700; font-size: var(--text-xs); font-family: var(--mono); }

/* 1-2e balancer: a ledger tile reads green when its atom counts match (the text says = or ≠ too, so colour is never the only signal) */
.readout[data-match="true"] .readout-value { color: var(--good); }

/* ============================================================
   UNIT 2 TOOLS (4c stage 3). The rules the six Unit 2 lessons' tools and figures need,
   and nothing else. Colours and sizes are tokens, and anything that follows the data is a
   data attribute (data-level, data-limiting, data-result, data-match), never a style write.
   ============================================================ */

/* stage shapes: a wide strip (1-7b), and two chambers that stack on a phone (2-6a) */
.sim-stage[data-ratio="strip"] { aspect-ratio: 12 / 5; }
.sim-stage[data-ratio="pair"] { aspect-ratio: 33 / 10; }
@media (max-width: 560px) { .sim-stage[data-ratio="pair"] { aspect-ratio: 3 / 4; } }
.sim-controls .tool-field { flex: 1 1 14rem; }

/* 1-7a: the formula box */
.formula-input { width: 100%; min-height: 44px; padding: 0.6rem 0.8rem; font-family: var(--mono); font-size: var(--text-md); color: var(--ink); background: var(--paper); border: 1px solid var(--hair); border-radius: var(--r-ctl); }
.formula-input:focus { outline: none; border-color: var(--ink); }

/* 1-7b: a conversion factor written as a fraction (in the lesson text and on the cards), and the setup line */
.fraction { display: inline-flex; flex-direction: column; align-items: center; vertical-align: middle; font-family: var(--mono); font-size: var(--text-base); line-height: 1.3; text-align: center; }
.fraction .numerator { padding: 0 0.4em 0.2em; border-bottom: 1.8px solid currentColor; }
.fraction .denominator { padding: 0.2em 0.4em 0; }
.canceled { text-decoration: line-through; text-decoration-color: var(--accent); text-decoration-thickness: 2px; color: var(--ink-soft); }
.setup-row { display: flex; flex-wrap: wrap; align-items: center; gap: 0.6rem 0.9rem; padding: 0.9rem 1rem; font-family: var(--mono); font-size: var(--text-lg); background: var(--paper); border: 1px solid var(--hair); border-radius: var(--r-ctl); }
.setup-item { font-weight: 700; }
.setup-item .unit-text { font-size: var(--text-base); font-weight: 600; }
.setup-op { font-weight: 700; color: var(--ink-mute); }
.slot-box { display: flex; align-items: center; justify-content: center; min-width: 9rem; min-height: 3.5rem; padding: 0.4rem 0.9rem; font-family: var(--display); font-size: var(--text-base); color: var(--ink-mute); background: var(--card); border: 2px dashed var(--hair); border-radius: var(--r-ctl); }
.slot-box[data-filled="true"] { color: var(--ink); background: var(--paper); border-style: solid; border-color: var(--ink); }
.factor-card { display: inline-flex; align-items: center; justify-content: center; min-width: 8.5rem; min-height: 4.5rem; padding: 0.5rem 0.9rem; font-family: var(--mono); font-size: var(--text-base); color: var(--ink); background: var(--card); border: 1.5px solid var(--hair); border-radius: var(--r-ctl); cursor: pointer; }
.factor-card:hover { border-color: var(--ink); }
.factor-card[aria-pressed="true"] { background: var(--paper-2); border-color: var(--ink); box-shadow: inset 0 0 0 1px var(--ink); }
.factor-card:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* 1-7c: the Before-Change-After table, the equation line, and the s'mores factory */
.bca-table { width: 100%; min-width: 520px; table-layout: fixed; border-collapse: collapse; font-family: var(--mono); font-size: var(--text-base); text-align: center; }
.bca-table th { padding: 0.65rem 0.5rem; font-weight: 700; color: var(--ink); border-bottom: 1.8px solid var(--ink); }
.bca-table th.rxn-header { font-family: var(--display); color: var(--accent); text-align: left; }
.bca-table th:first-child, .bca-table td:first-child { width: 24%; text-align: left; }
.bca-table th:not(:first-child), .bca-table td:not(:first-child) { width: 19%; text-align: center; }
.bca-table td { padding: 0.75rem 0.5rem; color: var(--ink-soft); vertical-align: middle; border-bottom: 1px solid var(--hair-soft); }
.bca-table td.row-label { font-family: var(--display); font-size: var(--text-xs); font-weight: 700; text-align: left; text-transform: uppercase; letter-spacing: 0.05em; color: var(--ink-mute); }
.bca-table td.input-val { font-weight: 700; color: var(--ink); }
.bca-table td[data-limiting="true"] { font-weight: 700; color: var(--accent); background: var(--accent-soft); }
.bca-table .placeholder-dash { color: var(--ink-mute); opacity: 0.5; }
.equation-display { display: block; margin: 1.5rem 0; padding: 1.25rem 1rem; font-family: var(--mono); font-size: var(--text-2xl); line-height: 1.4; text-align: center; background: var(--paper-2); border: 1px solid var(--hair-soft); border-radius: 4px; }
.equation-display .coeff { font-weight: 700; color: var(--accent); }
.equation-display sub { font-size: var(--text-base); line-height: 0; vertical-align: sub; }
.smor-bars { display: grid; gap: 0.75rem; margin: 1rem 0; }
.smor-bar { display: grid; grid-template-columns: 11rem 1fr 4.5rem; align-items: center; gap: 0.75rem; }
.smor-track { height: 10px; overflow: hidden; background: var(--hair-soft); border-radius: 5px; }
.smor-fill { width: 0; height: 100%; background: var(--hair); transition: width 0.3s ease; }
.smor-bar[data-limiting="true"] .smor-fill { background: var(--accent); }
.smor-ratio { font-family: var(--mono); font-size: var(--text-sm); color: var(--ink-soft); }
.smor-bar[data-level="0"] .smor-fill { width: 0.0%; }
.smor-bar[data-level="1"] .smor-fill { width: 8.33%; }
.smor-bar[data-level="2"] .smor-fill { width: 16.67%; }
.smor-bar[data-level="3"] .smor-fill { width: 25.0%; }
.smor-bar[data-level="4"] .smor-fill { width: 33.33%; }
.smor-bar[data-level="5"] .smor-fill { width: 41.67%; }
.smor-bar[data-level="6"] .smor-fill { width: 50.0%; }
.smor-bar[data-level="7"] .smor-fill { width: 58.33%; }
.smor-bar[data-level="8"] .smor-fill { width: 66.67%; }
.smor-bar[data-level="9"] .smor-fill { width: 75.0%; }
.smor-bar[data-level="10"] .smor-fill { width: 83.33%; }
.smor-bar[data-level="11"] .smor-fill { width: 91.67%; }
.smor-bar[data-level="12"] .smor-fill { width: 100.0%; }
.smor-tray { display: flex; flex-wrap: wrap; align-items: center; gap: 0.5rem; margin: 0.8rem 0; padding-top: 0.8rem; border-top: 1px dashed var(--hair-soft); }
.smor-chip { display: inline-flex; align-items: center; gap: 0.4rem; padding: 0.2rem 0.6rem; font-family: var(--mono); font-size: var(--text-xs); font-weight: 600; color: var(--ink); background: var(--paper-3); border: 1px solid var(--hair); border-radius: var(--r-tag); }
.smor-chip::before { content: ''; width: 0.8rem; height: 0.55rem; background: var(--ink-mute); border-radius: 2px; }
.smor-chip[data-kind="smore"]::before, .smor-chip[data-kind="graham"]::before { background: var(--warn); }
.smor-chip[data-kind="marsh"]::before { background: var(--paper-3); border: 1px solid var(--ink-mute); }
.smor-chip[data-kind="choco"]::before { background: var(--ink); }
.smor-chip[data-spare="true"] { background: var(--paper-2); border-style: dashed; color: var(--ink-soft); }
@media (max-width: 560px) { .smor-bar { grid-template-columns: 1fr 4.5rem; } .smor-bar .label { grid-column: 1 / -1; } }
@media (prefers-reduced-motion: reduce) { .smor-fill { transition: none; } }

/* 2-6a: the argument builders and the can/cannot card */
.argument-steps { display: grid; gap: 1rem; }
.step-header { display: block; margin-bottom: 0.35rem; font-family: var(--display); font-size: var(--text-xs); font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-mute); }
.step-select[data-result="ok"] { border-color: var(--good); background: var(--paper-3); }
.step-select[data-result="no"] { border-color: var(--accent); }
.paragraph-output { min-height: 6rem; padding: 1.2rem; background: var(--paper-2); border: 1px dashed var(--hair); border-radius: var(--r-ctl); }
.paragraph-output p { font-family: var(--serif); font-size: var(--text-base); line-height: 1.55; color: var(--ink-soft); }
.paragraph-output span[data-result="ok"] { color: var(--ink); }
.paragraph-output span[data-result="no"] { color: var(--ink); text-decoration: underline dotted var(--accent); text-decoration-thickness: 2px; }
.arg-missing { color: var(--ink-mute); }
.predict-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr)); gap: 1rem; margin: 1rem 0; }
.predict-can, .predict-cannot { padding: 1rem; border: 1px solid var(--hair); border-radius: var(--r-ctl); }
.predict-can { border-color: var(--good); background: color-mix(in srgb, var(--good) 8%, var(--card)); }
.predict-cannot { border-color: var(--accent); background: color-mix(in srgb, var(--accent) 8%, var(--card)); }
.predict-can h4, .predict-cannot h4 { margin: 0 0 0.5rem; }
.slider-row .side { font-size: var(--text-sm); font-weight: 400; color: var(--ink-mute); }
.argument-step { min-width: 0; }

/* ============================================================
   UNIT 3 TOOLS (4c stage 4). The rules the five Unit 3 lessons' tools need, and nothing else.
   Colours and sizes are tokens, and anything that follows the data is a data attribute.
   ============================================================ */

/* legend swatches for the greys the Unit 3 stages draw with */
.sim-legend .key[data-token="ink-soft"] { border-color: var(--ink-soft); }
.sim-legend .key[data-token="ink-mute"] { border-color: var(--ink-mute); }
.sim-legend .key[data-shape="dot"][data-token="ink-soft"], .sim-legend .key[data-shape="square"][data-token="ink-soft"] { background: var(--ink-soft); }
.sim-legend .key[data-shape="dot"][data-token="ink-mute"], .sim-legend .key[data-shape="square"][data-token="ink-mute"] { background: var(--ink-mute); }

/* 3-1a and 3-1b: the step-by-step working under a calculator */
.calc-steps { padding: 1rem 1.1rem; font-family: var(--mono); font-size: var(--text-base); line-height: 1.6; color: var(--ink); background: var(--paper); border: 1px solid var(--hair); border-radius: var(--r-ctl); }
.calc-steps p { margin: 0 0 0.6rem; }
.calc-steps p:last-child { margin-bottom: 0; }
.calc-steps .calc-result { padding-top: 0.6rem; font-size: var(--text-lg); font-weight: 700; border-top: 1px solid var(--ink); }
.calc-stage-list { margin: 0 0 0.8rem; padding-left: 1.4em; }
.calc-stage-list li { margin: 0 0 0.7rem; padding-left: 0.4rem; border-left: 3px solid var(--ink-mute); }
.calc-stage-list li[data-kind="plateau"] { border-left-color: var(--accent); }

/* 3-1c: the "Show the working" drawer under the calorimeter */
.derivation { margin: 0.4rem 0; }
.derivation summary { cursor: pointer; font-family: var(--display); font-size: var(--text-base); font-weight: 600; color: var(--ink); min-height: 44px; display: flex; align-items: center; }

/* 3-4a: the Enrichment tag stays readable inside a pressed chip (the chip turns ink-filled) */
.chip[aria-pressed="true"] .tag-enrichment { color: inherit; border-color: currentColor; }

/* 1-4a (file 3-14a): the bond-energy calculator's two columns */
.bond-cols { display: grid; grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr)); gap: 1rem; }
.bond-col { padding: 1rem 1.1rem; background: var(--paper); border: 1.5px solid var(--hair); border-radius: var(--r-ctl); }
.bond-col[data-side="broken"] { border-color: var(--accent); }
.bond-col[data-side="formed"] { border-color: var(--good); }
.bond-col ul { margin: 0.4rem 0 0; padding-left: 1.2em; font-family: var(--mono); font-size: var(--text-base); line-height: 1.6; }

/* ============================================================
   UNIT 4 TOOLS (4c stage 5). The rules the four Unit 4 lessons' tools and text need, and nothing else.
   Colours and sizes are tokens, and anything that follows the data is a data attribute.
   ============================================================ */

/* 4-6b: a one-line equation set inside a lever (CO2 + H2O -> H+ + HCO3-) */
.eq-line { font-family: var(--mono); font-weight: 700; color: var(--ink); }