/* ── Reset & Tokens ─── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  /* ── Background layers ── */
  --bg:        #0d1117;
  --surface:   #161b27;
  --surface2:  #1f2535;
  --border:    #2a3050;

  /* ── Accent — Polymer Simulator (polymer pink) ── */
  --accent:    #ec4899;
  --accent-lo: rgba(236,72,153,.22);

  /* ── Semantic colours — DO NOT CHANGE ── */
  --green:     #3ddc84;
  --red:       #ff5555;
  --gold:      #f5c842;

  /* ── Typography ── */
  --text:      #dde3f0;
  --text-dim:  #6b7a99;
  --font:      'Segoe UI', system-ui, sans-serif;
  --mono:      'Courier New', monospace;

  /* ── Layout ── */
  --radius:    12px;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  min-height: 100vh;
  padding: 0 16px;
}

#app { max-width: 1400px; margin: 0 auto; display: flex; flex-direction: column; gap: 14px; }

/* ── Header ─── */
header { text-align: center; padding: 4px 0; }
header h1 {
  font-size: 1.8rem; font-weight: 700;
  background: linear-gradient(120deg, #e53935 0%, #ff7043 100%);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.subtitle { color: var(--text-dim); font-size: 0.85rem; margin-top: 3px; }

/* ── Controls bar ─── */
.controls-bar {
  display: flex; flex-wrap: wrap; align-items: center; gap: 14px;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.ctrl-group  { display: flex; align-items: center; gap: 8px; }
.ctrl-label  { font-size: 0.72rem; text-transform: uppercase; letter-spacing: .06em; color: var(--text-dim); white-space: nowrap; }
.ctrl-value  { font-size: 0.82rem; color: var(--accent); font-weight: 600; min-width: 40px; }

/* ── Pill tabs ─── */
.pill-tabs { display: flex; background: var(--bg); border-radius: 8px; padding: 3px; gap: 2px; }
.pill {
  padding: 5px 13px; border: none; background: transparent; color: var(--text-dim);
  border-radius: 6px; cursor: pointer; font-size: 0.81rem;
  transition: background .18s, color .18s, box-shadow .18s;
}
.pill.active { background: var(--accent); color: #fff; box-shadow: 0 0 12px var(--accent-lo); }
.pill:hover:not(.active) { background: var(--surface2); color: var(--text); }

/* ── Buttons ─── */
.btn { padding: 8px 18px; border: none; border-radius: 8px; cursor: pointer; font-size: 0.84rem; font-weight: 600; transition: filter .18s, box-shadow .18s, opacity .18s; }
.btn:disabled { opacity: 0.38; cursor: not-allowed; }
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:not(:disabled):hover { filter: brightness(1.12); box-shadow: 0 0 12px var(--accent-lo); }
.btn-ghost { background: var(--surface2); color: var(--text); border: 1px solid var(--border); }
.btn-ghost:hover { background: var(--border); }

/* ── Sliders ─── */
input[type="range"] {
  -webkit-appearance: none; appearance: none;
  width: 120px; height: 6px;
  background: var(--surface2); border-radius: 3px; outline: none;
}
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none;
  width: 16px; height: 16px; border-radius: 50%;
  background: var(--accent); cursor: pointer;
  box-shadow: 0 0 6px var(--accent-lo);
}

/* ── Canvas card ─── */
.canvas-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 10px;
  overflow-x: clip;
}
.canvas-card canvas { display: block; width: 100%; height: auto; touch-action: pan-y; }

/* ── Readout panel ─── */
.readout-panel {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  gap: 8px;
}
.readout-cell {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 10px 14px;
  display: flex; flex-direction: column; gap: 2px;
}
.readout-label { font-size: 0.7rem; text-transform: uppercase; letter-spacing: .06em; color: var(--text-dim); }
.readout-value { font-size: 1.05rem; font-weight: 700; color: var(--text); font-family: var(--mono); }

/* ── Explore panel ─── */
.explore-tabs {
  display: flex; background: var(--bg); border-radius: 8px; padding: 3px; gap: 2px;
  flex-wrap: wrap; margin-bottom: 12px;
}
.concept-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 12px;
}
.concept-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px;
  transition: border-color .2s;
}
.concept-card:hover { border-color: var(--accent); }
.concept-card h3 { font-size: 0.95rem; color: var(--accent); margin-bottom: 4px; }
.concept-card .cc-formula {
  font-family: var(--mono); font-size: 0.82rem;
  background: var(--surface2); padding: 6px 10px; border-radius: 6px;
  margin: 8px 0; color: var(--gold);
}
.concept-card .cc-desc { font-size: 0.82rem; color: var(--text-dim); line-height: 1.45; }
.concept-card .cc-example {
  margin-top: 10px; padding: 10px; background: var(--bg);
  border-radius: 8px; border-left: 3px solid var(--accent);
}
.concept-card .cc-example-title { font-size: 0.72rem; text-transform: uppercase; color: var(--accent); margin-bottom: 4px; }
.concept-card .cc-example p { font-size: 0.8rem; color: var(--text-dim); margin: 2px 0; }

/* ── Practice panel ─── */
.practice-bar {
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.practice-prompt { font-size: 0.9rem; flex: 1 1 100%; margin-bottom: 4px; line-height: 1.5; }
.practice-input-group { display: flex; align-items: center; gap: 6px; }
.practice-input-group input {
  width: 120px; padding: 6px 10px; border-radius: 6px;
  border: 1px solid var(--border); background: var(--surface2);
  color: var(--text); font-size: 0.9rem; font-family: var(--mono);
}
.practice-unit { font-size: 0.82rem; color: var(--text-dim); }
.pbar-score { font-size: 0.84rem; color: var(--text-dim); margin-left: auto; }
.pbar-score span { color: var(--text); font-weight: 700; }
.feedback { margin-top: 6px; padding: 0 16px; min-height: 22px; }
.feedback.ok  { color: var(--green); font-size: 0.88rem; font-weight: 600; }
.feedback.err { color: var(--red);   font-size: 0.88rem; font-weight: 600; }
.solution-panel {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 14px 18px;
  font-size: 0.85rem; line-height: 1.6; color: var(--text-dim);
}
.solution-panel .step { margin: 4px 0; }
.solution-panel .step-num { color: var(--accent); font-weight: 600; }

/* ── Quiz panel ─── */
.quiz-bar {
  padding: 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.quiz-counter { font-size: 0.78rem; color: var(--text-dim); text-transform: uppercase; letter-spacing: .08em; }
.quiz-prompt { display: block; font-size: 0.95rem; margin: 10px 0; line-height: 1.5; }
.quiz-options { display: flex; flex-direction: column; gap: 6px; margin: 8px 0; }
.quiz-opt {
  padding: 10px 14px; border-radius: 8px; cursor: pointer;
  background: var(--surface2); border: 1px solid var(--border);
  color: var(--text); font-size: 0.88rem; transition: border-color .2s;
  text-align: left;
}
.quiz-opt:hover { border-color: var(--accent); }
.quiz-opt.selected { border-color: var(--accent); background: var(--accent-lo); }
.quiz-opt.correct { border-color: var(--green); background: rgba(61,220,132,.15); }
.quiz-opt.wrong { border-color: var(--red); background: rgba(255,85,85,.15); }
.quiz-input-group { display: flex; align-items: center; gap: 6px; margin: 8px 0; }
.quiz-input-group input {
  width: 140px; padding: 6px 10px; border-radius: 6px;
  border: 1px solid var(--border); background: var(--surface2);
  color: var(--text); font-size: 0.9rem; font-family: var(--mono);
}
.quiz-unit { font-size: 0.82rem; color: var(--text-dim); }
.quiz-actions { display: flex; gap: 10px; margin-top: 10px; }

/* ── Quiz result ─── */
.quiz-result {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 20px 22px;
}
.qr-header { text-align: center; margin-bottom: 16px; }
.qr-score { font-size: 2rem; font-weight: 700; }
.qr-score.perfect { color: var(--gold); }
.qr-score.good    { color: var(--green); }
.qr-score.poor    { color: var(--red); }
.qr-stars { font-size: 1.4rem; margin-top: 4px; }
.qr-rows { display: flex; flex-direction: column; gap: 6px; margin-top: 12px; }
.qr-row {
  display: flex; justify-content: space-between; align-items: center;
  padding: 8px 12px; border-radius: 8px; background: var(--surface2);
  font-size: 0.84rem;
}
.qr-row.ok  { border-left: 3px solid var(--green); }
.qr-row.err { border-left: 3px solid var(--red); }
.qr-row .qr-q { flex: 1; color: var(--text-dim); }
.qr-row .qr-a { color: var(--text); font-weight: 600; margin: 0 10px; }
.qr-row .qr-icon { font-size: 1rem; }
.qr-retry { text-align: center; margin-top: 14px; }

/* ── SEO article ─── */
.seo-article {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 28px 24px; line-height: 1.7;
}
.seo-article h2 { font-size: 1.3rem; color: var(--accent); margin-bottom: 12px; }
.seo-article h3 { font-size: 1.05rem; color: var(--text); margin: 18px 0 8px; }
.seo-article p { font-size: 0.92rem; color: var(--text-dim); margin-bottom: 10px; }
.seo-article a { color: var(--accent); text-decoration: none; }
.seo-article a:hover { text-decoration: underline; }

/* ── Responsive ──────────────────────────────────────────────── */

@media (max-width: 768px) {
  .readout-panel { grid-template-columns: repeat(3, 1fr); }
  .controls-bar { gap: 10px; }
  input[type="range"] { width: 90px; }
  .concept-grid { grid-template-columns: 1fr; }
}

@media (max-width: 500px) {
  header h1 { font-size: 1.4rem; }
  .subtitle  { font-size: 0.78rem; }
  .controls-bar { padding: 10px 12px; gap: 8px; }
  .pill { padding: 5px 10px; font-size: 0.76rem; }
  .readout-panel { grid-template-columns: repeat(2, 1fr); }
  input[type="range"] { width: 70px; }
  .practice-bar { flex-direction: column; align-items: stretch; }
  .pbar-score { margin-left: 0; }
}

/* INTERLINK-START  header quick-links */
.head-actions{display:flex;align-items:center;gap:8px;margin-left:auto;flex-wrap:wrap;justify-content:flex-end;}
.btn-link{display:inline-flex;align-items:center;gap:7px;padding:5px 12px;border-radius:8px;font-size:.82rem;font-weight:700;text-decoration:none;cursor:pointer;background:var(--surface2,#1f2535);color:var(--text,#dde3f0);border:1.5px solid var(--border,#2a3050);white-space:nowrap;transition:border-color .18s,background .18s,color .18s;}
.btn-link:hover{border-color:var(--accent,#4fc3f7);background:var(--accent-lo,rgba(79,195,247,.18));color:#fff;}
.btn-link img{width:20px;height:20px;border-radius:4px;flex:none;}
.btn-link .lbl{line-height:1;}
@media(max-width:560px){.btn-link .lbl{display:none;}.btn-link{padding:5px 9px;}}
/* With a third quick-link (Gearbox) the row overflowed by ~17 px and
   wrapped under the mode tabs — at every width, since #app caps the bar.
   Share keeps its icon and word; only the trailing "your setup" goes, as
   site.css already does below 640 px. */
.head-actions .btn-share-ext { display: none; }
/* ...and on a 1024-1100 px window it still did not fit, so the quick-links
   go icon-only there (title + aria-label keep the name), as they already
   do below 560 px. Wider than 1100 px the labels return. */
@media (max-width: 1100px) { .btn-link .lbl { display: none; } .btn-link { padding: 5px 9px; } }
/* INTERLINK-END */

/* ── Display Controls — collapsible overlay pinned to the canvas ── */
.canvas-toggles {
  position: absolute; top: 16px; left: 16px; z-index: 4;
  background: rgba(13,17,23,0.88);
  -webkit-backdrop-filter: blur(3px); backdrop-filter: blur(3px);
  border: 1px solid var(--border); border-radius: 9px;
  box-shadow: 0 4px 14px rgba(0,0,0,0.35);
  max-width: calc(100% - 32px);
}
.canvas-toggles > summary {
  list-style: none; cursor: pointer; user-select: none;
  display: flex; align-items: center; justify-content: center; gap: 0;
  padding: 0; white-space: nowrap;
  width: 34px; height: 34px;
  font-size: 0.66rem; font-weight: 700; text-transform: uppercase; letter-spacing: .05em;
  color: var(--text); border-radius: 9px; transition: background .12s, color .12s;
}
.canvas-toggles > summary .cvt-title,
.canvas-toggles > summary .cvt-caret { display: none; }
.canvas-toggles .cvt-ico { width: 17px; height: 17px; }
/* Opened, it earns its caption back — the user has chosen to cover the canvas. */
.canvas-toggles[open] > summary {
  width: auto; height: auto; min-height: 30px;
  padding: 6px 10px; gap: 7px; justify-content: flex-start;
}
.canvas-toggles[open] > summary .cvt-title { display: inline; }
.canvas-toggles[open] > summary .cvt-caret { display: inline; }
.canvas-toggles > summary::-webkit-details-marker { display: none; }
.canvas-toggles > summary::marker { content: ''; }
.canvas-toggles > summary:hover { background: var(--accent-lo); color: var(--accent); }
.canvas-toggles > summary:focus-visible { outline: 2px solid var(--gold); outline-offset: 2px; }
.canvas-toggles .cvt-ico { flex-shrink: 0; color: var(--accent); }
.canvas-toggles .cvt-caret {
  margin-left: auto; padding-left: 4px; color: var(--text-dim);
  font-size: 0.7rem; transition: transform .2s;
}
.canvas-toggles[open] > summary .cvt-caret { transform: rotate(180deg); color: var(--accent); }
.canvas-toggles[open] > summary {
  border-bottom: 1px solid var(--border); border-radius: 9px 9px 0 0;
}
.canvas-toggles .cvt-body {
  display: flex; flex-direction: column; gap: 5px;
  padding: 8px 11px 10px; max-height: 60vh; overflow-y: auto;
}
.canvas-toggles .cvt-group {
  font-size: 0.58rem; font-weight: 800; letter-spacing: .09em;
  text-transform: uppercase; color: var(--accent);
  margin-top: 4px; padding-bottom: 2px; border-bottom: 1px solid var(--border);
}
.canvas-toggles .cvt-group:first-child { margin-top: 0; }
.canvas-toggles .cvt-item {
  display: flex; align-items: center; gap: 6px;
  font-size: 0.72rem; color: var(--text-dim); cursor: pointer;
  white-space: nowrap; transition: color .12s;
}
.canvas-toggles .cvt-item:hover { color: var(--text); }
.canvas-toggles .cvt-item input[type="checkbox"] {
  accent-color: var(--accent); width: 14px; height: 14px; cursor: pointer; flex-shrink: 0;
}
.canvas-toggles .cvt-reset {
  margin-top: 7px; padding: 5px 9px; min-height: 28px;
  background: var(--surface2); border: 1px solid var(--border); border-radius: 6px;
  color: var(--text-dim); font-size: 0.66rem; font-weight: 700;
  text-transform: uppercase; letter-spacing: .05em; cursor: pointer;
  transition: border-color .12s, color .12s;
}
.canvas-toggles .cvt-reset:hover { border-color: var(--accent); color: var(--accent); }
.canvas-toggles .cvt-reset:focus-visible { outline: 2px solid var(--gold); outline-offset: 2px; }


/* ═══════════════════════════════════════════════════════════════════
   Polymer Simulator — Build Your Atom layout: canvas left, info rail right
   ═══════════════════════════════════════════════════════════════════ */
.sim-layout { display: grid; grid-template-columns: minmax(0, 1fr) 420px; gap: 14px; }
.sim-left { display: flex; flex-direction: column; gap: 12px; min-width: 0; }
.canvas-card { position: relative; overflow-x: clip; padding: 10px; }

/* identity strip above the canvas */
.poly-strip {
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
  padding: 8px 12px; margin-bottom: 8px;
  background: var(--surface2); border: 1px solid var(--border); border-radius: 10px;
}
.ps-identity { min-width: 0; }
.ps-name { font-size: 1.05rem; font-weight: 800; color: var(--text); line-height: 1.2; }
.ps-iupac { font-size: 0.76rem; color: var(--text-dim); }
.ps-unit { font-family: var(--mono); font-size: 1rem; font-weight: 700; color: var(--accent); white-space: nowrap; }
.ps-badges { display: flex; gap: 6px; flex-wrap: wrap; margin-left: auto; }
.ps-badge { font-size: 0.66rem; font-weight: 800; text-transform: uppercase; letter-spacing: .06em; padding: 3px 8px; border-radius: 6px; background: var(--accent-lo); color: var(--accent); white-space: nowrap; }
.ps-badge.alt { background: rgba(79,195,247,.16); color: #4fc3f7; }
.ps-badge.warn { background: rgba(245,200,66,.14); color: var(--gold); }

.canvas-wrap { position: relative; }
#lab-canvas { display: block; width: 100%; height: auto; aspect-ratio: 1000 / 600; border-radius: 8px; touch-action: pan-y; }
.ps3d-stage { position: absolute; inset: 0; border-radius: 8px; overflow: hidden; }
.ps3d-stage[hidden] { display: none; }
.ps3d-stage canvas { display: block; width: 100%; height: 100%; }
.ps3d-note {
  position: absolute; left: 50%; bottom: 12px; transform: translateX(-50%); z-index: 7;
  background: rgba(13,17,23,.92); border: 1px solid var(--border); border-radius: 8px;
  padding: 6px 10px; font-size: 0.76rem; color: var(--text); display: flex; gap: 8px; align-items: center;
}
.ps3d-note[hidden] { display: none; }
.ps3d-note button { background: none; border: none; color: var(--text-dim); cursor: pointer; font-size: 0.9rem; min-width: 28px; min-height: 28px; }

.canvas-overlay-toggles { position: absolute; top: 16px; right: 16px; z-index: 5; display: flex; flex-direction: column; align-items: flex-end; gap: 6px; }
.vt-tabs {
  display: flex; gap: 2px; padding: 3px; border-radius: 20px;
  background: rgba(13,17,23,0.82); border: 1px solid rgba(236,72,153,.35);
  -webkit-backdrop-filter: blur(6px); backdrop-filter: blur(6px);
}
.vt-tabs[hidden] { display: none; }
.vt-pill {
  display: inline-flex; align-items: center; gap: 5px;
  padding: 5px 12px; min-height: 30px; border: none; border-radius: 16px; background: transparent;
  color: var(--text-dim); font-family: var(--font); font-size: 0.76rem; font-weight: 700; cursor: pointer;
  transition: background .12s, color .12s;
}
.vt-pill:hover:not([aria-pressed="true"]) { background: var(--surface2); color: var(--text); }
.vt-pill[aria-pressed="true"] { background: var(--accent); color: #fff; box-shadow: 0 0 10px var(--accent-lo); }
.vt-pill:focus-visible { outline: 2px solid var(--gold); outline-offset: 1px; }

.fs-btn {
  position: absolute; bottom: 14px; right: 14px; z-index: 6;
  display: inline-flex; align-items: center; gap: 6px; padding: 6px 12px; min-height: 32px;
  background: rgba(13,17,23,0.78); border: 1px solid var(--border); color: var(--text-dim);
  border-radius: 20px; font-size: .76rem; font-weight: 600; cursor: pointer; user-select: none;
  -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px); transition: all .15s;
}
.fs-btn:hover { background: var(--accent-lo); border-color: var(--accent); color: var(--accent); }
.fs-btn:focus-visible { outline: 2px solid var(--gold); outline-offset: 2px; }
.fs-icon { display: inline-flex; }
.fs-icon-exit { display: none; }
body.ps-focus .fs-icon-enter { display: none; }
body.ps-focus .fs-icon-exit { display: inline-flex; }

.status-line { font-size: 0.8rem; color: var(--text-dim); line-height: 1.45; padding: 8px 4px 0; min-height: 1.45em; }
.action-bar { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; padding: 8px 4px 0; }
.action-bar .btn { padding: 6px 12px; font-size: .8rem; min-height: 32px; }
.action-bar .btn-exp { margin-left: auto; }

/* the controls dock under the canvas */
.bench-dock {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 12px 14px; display: flex; flex-direction: column; gap: 12px;
}
.bench-dock[hidden] { display: none; }
.action-row { display: flex; gap: 8px; flex-wrap: wrap; }
.mono-groups { display: flex; flex-direction: column; gap: 8px; }
.mono-group { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.mono-group .ctrl-label { min-width: 104px; }
.mono-pills { display: flex; flex-wrap: wrap; gap: 4px; }
.mono-pill {
  padding: 5px 10px; min-height: 30px; border-radius: 7px; border: 1px solid var(--border);
  background: var(--surface2); color: var(--text-dim); font-family: var(--font);
  font-size: 0.76rem; font-weight: 600; cursor: pointer; transition: border-color .12s, color .12s, background .12s;
}
.mono-pill:hover { color: var(--text); border-color: var(--accent); }
.mono-pill[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: #fff; }
.mono-pill:focus-visible { outline: 2px solid var(--gold); outline-offset: 1px; }
.custom-subs { display: flex; align-items: center; gap: 6px; flex-wrap: wrap; }
.custom-subs[hidden] { display: none; }
.custom-subs select, #struct-polymer { background: var(--surface2); color: var(--text); border: 1px solid var(--border); border-radius: 6px; padding: 4px 8px; font-size: 0.8rem; min-height: 32px; }
.cs-eq { font-weight: 700; color: var(--accent); }
.param-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 10px 18px; }
.param { display: flex; flex-direction: column; gap: 4px; min-width: 0; }
.param[hidden] { display: none; }
.p-cap { font-size: 0.74rem; color: var(--text-dim); display: flex; justify-content: space-between; gap: 8px; }
.p-cap output { color: var(--accent); font-weight: 700; font-family: var(--mono); }
.param input[type="range"] { width: 100%; }

/* the rail */
.info-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px; display: flex; flex-direction: column; gap: 10px; min-width: 0;
}
.poly-card-big { background: var(--surface2); border: 1px solid var(--border); border-radius: 10px; padding: 10px 12px; display: flex; flex-direction: column; gap: 6px; }
.pc-type { font-size: 0.66rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); }
#unit-canvas { width: 100%; height: auto; aspect-ratio: 380 / 120; }
.pc-formula { font-family: var(--mono); font-size: 0.86rem; color: var(--text); }
.stats-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 6px; }
.stats-grid .readout-cell { padding: 7px 10px; }
.hist-card { background: var(--surface2); border: 1px solid var(--border); border-radius: 10px; padding: 8px 10px; }
.hist-card[hidden] { display: none; }
.hist-title { font-size: 0.7rem; font-weight: 800; letter-spacing: .07em; text-transform: uppercase; color: var(--text-dim); }
#hist-canvas { display: block; width: 100%; height: auto; aspect-ratio: 400 / 230; margin-top: 4px; }
.panel-note { font-size: 0.76rem; color: var(--text-dim); line-height: 1.5; }
.panel-note:empty { display: none; }

@media (max-width: 1100px) {
  .sim-layout { grid-template-columns: minmax(0, 1fr); }
  .info-panel { display: grid; grid-template-columns: 1fr 1fr; align-items: start; }
  .info-panel .panel-note { grid-column: 1 / -1; }
}
@media (max-width: 768px) {
  .info-panel { display: flex; }
  .fs-label { display: none; }
  .fs-btn { bottom: 8px; right: 8px; padding: 4px 9px; min-height: 30px; }
  .canvas-overlay-toggles { top: 8px; right: 8px; }
  .mono-group .ctrl-label { min-width: 0; flex: 1 1 100%; }
  .ps-badges { margin-left: 0; }
}
@media (max-width: 500px) {
  .vt-pill { padding: 4px 9px; font-size: 0.7rem; min-height: 28px; }
  .action-bar .btn-exp { margin-left: 0; }
  .stats-grid { grid-template-columns: 1fr 1fr; }
}

/* ══════════ FOCUS MODE (pseudo-fullscreen, as Build Your Atom) ══════════
   A fixed overlay rather than the Fullscreen API: the auto-ads anchor at <body>
   level keeps working, iPad Safari supports it, and a harness can reach it. */
body.ps-focus { overflow: hidden; }
body.ps-focus #sec-simulate.is-focus > *:not(.sim-layout) { display: none !important; }
#sec-simulate.is-focus {
  position: fixed; inset: 0; z-index: 900; display: grid; grid-template-rows: minmax(0, 1fr);
  padding: 12px 12px calc(12px + var(--fs-anchor, 0px));
  background: radial-gradient(ellipse at 50% 40%, #1d1230 0%, #0b0a16 60%, #06060d 100%);
  box-sizing: border-box; overflow: hidden;
}
#sec-simulate.is-focus .sim-layout { grid-template-columns: minmax(0, 1fr) 360px; height: 100%; min-height: 0; align-items: stretch; }
#sec-simulate.is-focus .sim-left { display: grid; grid-template-rows: minmax(0, 1fr) auto; min-height: 0; }
#sec-simulate.is-focus .canvas-card { display: flex; flex-direction: column; min-height: 0; padding: 8px; background: rgba(22,18,38,.6); }
#sec-simulate.is-focus .canvas-wrap { flex: 1 1 auto; min-height: 0; display: flex; align-items: center; justify-content: center; }
#sec-simulate.is-focus #lab-canvas { width: auto; height: 100%; max-width: 100%; max-height: 100%; }
#sec-simulate.is-focus .bench-dock { padding: 8px 12px; gap: 8px; max-height: 34vh; overflow-y: auto; }
#sec-simulate.is-focus .info-panel { min-height: 0; overflow-y: auto; overscroll-behavior: contain; padding: 10px; background: rgba(22,18,38,.6); }
@media (max-width: 1100px) {
  #sec-simulate.is-focus .sim-layout { grid-template-columns: minmax(0, 1fr); grid-template-rows: minmax(0, 1fr) auto; }
  #sec-simulate.is-focus .info-panel { display: none; }
}

/* Explore cards */
.explore-tabs { display: flex; gap: 4px; margin-bottom: 10px; }
.poly-card { display: flex; flex-direction: column; gap: 6px; }
.poly-card canvas { width: 100%; height: auto; aspect-ratio: 360 / 90; background: var(--bg); border-radius: 8px; }
.poly-props { display: grid; grid-template-columns: auto 1fr; gap: 2px 10px; font-size: 0.78rem; }
.poly-props dt { color: var(--text-dim); }
.poly-props dd { color: var(--text); font-family: var(--mono); }
.poly-tag { display: inline-block; font-size: 0.66rem; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; padding: 2px 7px; border-radius: 5px; background: var(--accent-lo); color: var(--accent); }

/* Practice */
.practice-options { display: flex; flex-direction: column; gap: 6px; flex: 1 1 100%; }
.practice-options:empty { display: none; }
.practice-actions { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.practice-actions select { background: var(--surface2); color: var(--text); border: 1px solid var(--border); border-radius: 6px; padding: 6px 8px; min-height: 34px; font-size: 0.8rem; }
.opt-btn {
  text-align: left; padding: 9px 12px; min-height: 40px; border-radius: 8px; border: 1px solid var(--border);
  background: var(--surface2); color: var(--text); font-family: var(--mono); font-size: 0.86rem; cursor: pointer;
}
.opt-btn[aria-pressed="true"] { border-color: var(--accent); background: var(--accent-lo); }
.opt-btn.right { border-color: var(--green); }
.opt-btn.wrong { border-color: var(--red); }


/* 3D chain view: a caption over the 3D canvas */
.ps3d-hud {
  position: absolute; left: 16px; bottom: 14px; z-index: 4; max-width: calc(100% - 150px);
  background: rgba(13,17,23,0.82); border: 1px solid var(--border); border-radius: 9px;
  padding: 6px 10px; font-size: 0.76rem; color: var(--text); line-height: 1.4;
}
.ps3d-hud span { display: block; color: var(--text-dim); font-size: 0.7rem; }
.ps3d-stage canvas { touch-action: pan-y; cursor: grab; }

/* On a phone the two canvas chips would cover the reaction; they sit in a row above the canvas instead. */
@media (max-width: 640px) {
  .canvas-wrap { display: flex; flex-direction: column; }
  .canvas-wrap > .canvas-toggles { position: relative; top: auto; left: auto; order: -2; align-self: flex-start; margin-bottom: 6px; }
  .canvas-wrap > .canvas-overlay-toggles { position: static; order: -1; flex-direction: row; align-items: center; align-self: flex-end; margin: -40px 0 6px; }
  .canvas-wrap > #lab-canvas { order: 0; }
}