/* ── page fill so sim canvas can go full-height ── */
    .app-layout  { height: 100vh; overflow: hidden; }
    .sb-content  { height: 100vh; display: flex; flex-direction: column; overflow: hidden; }

    /* ════════════════════════════════
       HOME VIEW
    ════════════════════════════════ */
    #lab-home { flex: 1; overflow-y: auto; padding: 36px 28px 80px; }

    .lab-hero {
      display: flex; align-items: center; gap: 20px;
      margin-bottom: 36px;
    }
    .lab-hero-icon {
      width: 64px; height: 64px; border-radius: 20px; flex-shrink: 0;
      background: linear-gradient(135deg, rgba(155,93,229,.35), rgba(6,214,224,.25));
      border: 1.5px solid rgba(255,255,255,.12);
      display: flex; align-items: center; justify-content: center;
    }
    .lab-hero-icon svg { width: 30px; height: 30px; stroke: var(--violet); stroke-width: 1.5; }
    .lab-hero-title {
      font-family: 'Unbounded', sans-serif; font-size: 1.55rem; font-weight: 800;
      letter-spacing: -0.02em; margin-bottom: 5px;
    }
    .lab-hero-sub { font-size: 0.9rem; color: var(--text-2); font-weight: 500; }

    /* category filter */
    .lab-filters {
      display: flex; gap: 6px; margin-bottom: 28px; flex-wrap: wrap;
    }
    .lab-filter {
      padding: 6px 18px; border-radius: 99px;
      border: 1.5px solid var(--border-h);
      background: var(--surface); color: var(--text-2);
      font-family: 'Manrope', sans-serif; font-size: 0.82rem; font-weight: 700;
      cursor: pointer; transition: all .16s;
    }
    .lab-filter:hover { border-color: rgba(155,93,229,.4); color: var(--violet); }
    .lab-filter.active { background: var(--text); color: #fff; border-color: var(--text); }

    /* sim grid */
    .sim-grid {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(270px, 1fr));
      gap: 20px;
    }

    .sim-card {
      background: var(--surface);
      border: 1.5px solid var(--border);
      border-radius: 20px;
      overflow: hidden;
      cursor: pointer;
      transition: border-color .18s, box-shadow .18s, transform .18s;
      position: relative;
    }
    .sim-card:hover {
      border-color: var(--violet);
      box-shadow: 0 8px 32px rgba(155,93,229,.18);
      transform: translateY(-2px);
    }
    .sim-card.soon { cursor: default; opacity: .65; }
    .sim-card.soon:hover { transform: none; box-shadow: none; border-color: var(--border); }

    .sim-preview {
      width: 100%; height: 140px; display: block;
      background: #0D0D1A;
    }

    .sim-body { padding: 18px 20px 20px; }
    .sim-cat {
      display: inline-flex; align-items: center; gap: 5px;
      font-size: 0.68rem; font-weight: 800; text-transform: uppercase; letter-spacing: .06em;
      padding: 3px 10px; border-radius: 99px; margin-bottom: 10px;
    }
    .sim-cat.math { background: rgba(155,93,229,.12); color: var(--violet); }
    .sim-cat.phys { background: rgba(6,214,224,.1);  color: var(--cyan); }

    .sim-title {
      font-family: 'Unbounded', sans-serif; font-size: 0.9rem; font-weight: 800;
      margin-bottom: 6px; letter-spacing: -.01em;
    }
    .sim-desc { font-size: 0.82rem; color: var(--text-2); line-height: 1.55; }

    .sim-soon-badge {
      position: absolute; top: 12px; right: 12px;
      background: rgba(15,23,42,.7); color: rgba(255,255,255,.55);
      font-size: 0.65rem; font-weight: 800; text-transform: uppercase; letter-spacing: .06em;
      padding: 3px 9px; border-radius: 99px; backdrop-filter: blur(6px);
      border: 1px solid rgba(255,255,255,.1);
    }

    /* ════════════════════════════════
       SIM VIEW (graph)
    ════════════════════════════════ */
    #lab-sim {
      display: none;
      flex: 1; min-height: 0;
      flex-direction: column;
    }
    #lab-sim.open { display: flex; }

    /* top bar */
    .sim-topbar {
      flex-shrink: 0;
      display: flex; align-items: center; gap: 12px;
      padding: 10px 18px;
      background: var(--surface);
      border-bottom: 1.5px solid var(--border);
    }
    .sim-back {
      display: flex; align-items: center; gap: 6px;
      padding: 6px 14px; border-radius: 99px;
      border: 1.5px solid var(--border-h);
      background: transparent; color: var(--text-2);
      font-family: 'Manrope', sans-serif; font-size: 0.82rem; font-weight: 700;
      cursor: pointer; transition: all .15s;
    }
    .sim-back:hover { border-color: var(--violet); color: var(--violet); }
    .sim-back svg { width: 14px; height: 14px; stroke: currentColor; stroke-width: 2.2; flex-shrink: 0; }

    .sim-topbar-title {
      font-family: 'Unbounded', sans-serif; font-size: 0.88rem; font-weight: 800;
      flex: 1;
    }

    .sim-zoom-btns { display: flex; gap: 4px; }
    .zoom-btn {
      min-width: 32px; width: auto; height: 32px; border-radius: 10px;
      border: 1.5px solid var(--border-h);
      background: transparent; color: var(--text-2);
      cursor: pointer; font-size: .8rem; font-weight: 700;
      padding: 0 9px; white-space: nowrap;
      display: flex; align-items: center; justify-content: center; gap: 4px;
      transition: all .15s;
    }
    .zoom-btn:hover { border-color: var(--violet); color: var(--violet); background: rgba(155,93,229,.07); }
    .zoom-btn svg { width: 15px; height: 15px; stroke: currentColor; stroke-width: 2.2; }

    /* sim body */
    .sim-body-wrap {
      flex: 1; min-height: 0;
      display: flex;
    }

    /* left panel */
    .graph-panel {
      width: 280px; flex-shrink: 0;
      background: var(--surface);
      border-right: 1.5px solid var(--border);
      display: flex; flex-direction: column;
      overflow-y: auto;
      padding: 16px 14px;
      gap: 6px;
    }

    .gp-section-title {
      font-family: 'Unbounded', sans-serif; font-size: 0.62rem; font-weight: 800;
      color: var(--text-3); text-transform: uppercase; letter-spacing: .08em;
      display: flex; align-items: center; gap: 8px; margin: 4px 0 8px;
    }
    .gp-section-title::after { content: ''; flex: 1; height: 1px; background: var(--border); }

    /* function rows */
    .fn-row {
      display: flex; align-items: center; gap: 8px;
      padding: 8px 10px; border-radius: 12px;
      border: 1.5px solid var(--border);
      background: rgba(15,23,42,.03);
      transition: border-color .15s;
    }
    .fn-label {
      font-family: 'Manrope', monospace; font-size: 0.85rem; font-weight: 700;
      color: var(--fn-color, var(--violet)); flex-shrink: 0; letter-spacing: .01em;
    }
    .fn-row:focus-within { border-color: var(--fn-color, var(--violet)); }

    .fn-dot {
      width: 12px; height: 12px; border-radius: 50%;
      flex-shrink: 0;
      background: var(--fn-color, var(--violet));
      box-shadow: 0 0 6px var(--fn-color, var(--violet));
    }
    .fn-input {
      flex: 1; border: none; outline: none; background: transparent;
      font-family: 'Manrope', monospace; font-size: 0.88rem; font-weight: 600;
      color: var(--text); padding: 0; min-width: 0;
    }
    .fn-input::placeholder { color: var(--text-3); font-weight: 500; }

    /* KaTeX live preview */
    .fn-preview {
      min-height: 20px; padding: 3px 4px 3px 36px;
      font-size: 0.82rem; line-height: 1.5;
      color: rgba(255,255,255,.65);
      overflow: hidden; display: none;
    }
    .fn-preview.has-content { display: block; }
    .fn-preview .katex { color: rgba(255,255,255,.8); font-size: 1em; }
    .fn-err {
      font-size: 0.68rem; color: var(--pink); font-weight: 600;
      padding: 2px 0 0 22px; display: none;
    }
    .fn-err.show { display: block; }

    /* presets */
    .presets-wrap { display: flex; flex-wrap: wrap; gap: 5px; }
    .preset-btn {
      padding: 4px 11px; border-radius: 8px;
      border: 1.5px solid var(--border-h);
      background: transparent; color: var(--text-2);
      font-family: 'Manrope', monospace; font-size: 0.75rem; font-weight: 700;
      cursor: pointer; transition: all .14s;
    }
    .preset-btn:hover {
      border-color: var(--violet); color: var(--violet);
      background: rgba(155,93,229,.07);
    }

    /* info / actions */
    .gp-btn {
      display: flex; align-items: center; justify-content: center; gap: 7px;
      padding: 9px 14px; border-radius: 12px;
      border: 1.5px solid var(--border-h);
      background: transparent; color: var(--text-2);
      font-family: 'Manrope', sans-serif; font-size: 0.82rem; font-weight: 700;
      cursor: pointer; transition: all .15s; width: 100%;
    }
    .gp-btn:hover { border-color: var(--violet); color: var(--violet); background: rgba(155,93,229,.06); }
    .gp-btn svg { width: 14px; height: 14px; stroke: currentColor; stroke-width: 2; flex-shrink: 0; }

    /* stereo param sliders */
    .stereo-sl-row { margin-bottom: 6px; }
    .stereo-sl-row label { display: flex; justify-content: space-between; font-size: 0.72rem; color: var(--text-2); margin-bottom: 2px; }
    .stereo-sl-row label span { color: var(--violet); font-weight: 700; }
    .stereo-sl-row input[type=range] { width: 100%; accent-color: var(--violet); }
    .stereo-fig-btn.active, .stereo-toggle.active, .stereo-sect-btn.active, .stereo-sect-type.active {
      border-color: var(--violet) !important; color: var(--violet) !important; background: rgba(155,93,229,.1) !important;
    }

    /* stereo panel redesign */
    .stereo-panel {
      width: 230px; flex-shrink: 0;
      background: var(--surface);
      border-right: 1.5px solid var(--border);
      display: flex; flex-direction: column;
      overflow-y: auto; padding: 10px 10px;
    }
    .stereo-fig-grid {
      display: grid; grid-template-columns: 1fr 1fr; gap: 3px;
      margin-bottom: 4px;
    }
    .st-fig-btn {
      display: flex; align-items: center; gap: 5px;
      padding: 6px 8px; border-radius: 9px;
      border: 1.5px solid var(--border);
      background: transparent; color: var(--text-2);
      font-family: 'Manrope', sans-serif; font-size: 0.68rem; font-weight: 700;
      cursor: pointer; transition: all .13s; white-space: nowrap; overflow: hidden;
    }
    .st-fig-btn svg { width: 13px; height: 13px; stroke: currentColor; stroke-width: 2; flex-shrink: 0; fill: none; }
    .st-fig-btn:hover { border-color: rgba(155,93,229,.4); color: var(--violet); background: rgba(155,93,229,.06); }
    .st-fig-btn.active { border-color: var(--violet); color: var(--violet); background: rgba(155,93,229,.12); }
    .st-fig-btn-wide { grid-column: span 2; }

    .st-tool-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 3px; margin-bottom: 4px; }
    .st-tool-btn {
      display: flex; align-items: center; gap: 5px;
      padding: 6px 8px; border-radius: 9px;
      border: 1.5px solid var(--border);
      background: transparent; color: var(--text-2);
      font-family: 'Manrope', sans-serif; font-size: 0.68rem; font-weight: 700;
      cursor: pointer; transition: all .13s; white-space: nowrap; overflow: hidden;
    }
    .st-tool-btn svg { width: 12px; height: 12px; stroke: currentColor; stroke-width: 2; flex-shrink: 0; fill: none; }
    .st-tool-btn:hover { border-color: rgba(155,93,229,.4); color: var(--violet); background: rgba(155,93,229,.06); }
    .st-tool-btn.active { border-color: var(--violet); color: var(--violet); background: rgba(155,93,229,.12); }
    .st-tool-btn-wide { grid-column: span 2; }

    .st-action-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 3px; margin-bottom: 2px; }
    .st-action-btn {
      padding: 5px 6px; border-radius: 8px;
      border: 1px solid var(--border);
      background: transparent; color: var(--text-2);
      font-family: 'Manrope', sans-serif; font-size: 0.65rem; font-weight: 600;
      cursor: pointer; transition: all .13s; text-align: center;
    }
    .st-action-btn:hover { border-color: rgba(239,71,111,.4); color: #ef476f; background: rgba(239,71,111,.06); }

    .st-toggle-row {
      display: flex; align-items: center; justify-content: space-between;
      padding: 4px 2px; cursor: pointer; transition: background .13s; border-radius: 7px;
    }
    .st-toggle-row:hover { background: rgba(255,255,255,.03); }
    .st-toggle-label {
      font-size: 0.7rem; font-weight: 600; color: var(--text-2);
      display: flex; align-items: center; gap: 5px;
    }
    .st-toggle-label svg { width: 11px; height: 11px; stroke: currentColor; stroke-width: 2; opacity: .6; fill: none; }
    .st-toggle {
      width: 26px; height: 14px; border-radius: 7px;
      background: rgba(255,255,255,.1); border: 1.5px solid var(--border-h);
      position: relative; transition: background .15s; flex-shrink: 0; cursor: pointer;
    }
    .st-toggle::after {
      content: ''; position: absolute; left: 2px; top: 50%;
      transform: translateY(-50%);
      width: 8px; height: 8px; border-radius: 50%;
      background: rgba(255,255,255,.4); transition: all .15s;
    }
    .st-toggle.on { background: var(--violet); border-color: var(--violet); }
    .st-toggle.on::after { left: calc(100% - 10px); background: #fff; }

    .st-n-ctrl {
      display: flex; align-items: center; gap: 5px;
      border: 1.5px solid var(--border); border-radius: 9px;
      padding: 4px 6px;
    }
    .st-n-btn {
      width: 20px; height: 20px; border-radius: 5px;
      border: 1px solid var(--border-h);
      background: transparent; color: var(--text-2);
      cursor: pointer; display: flex; align-items: center; justify-content: center;
      transition: background .12s;
    }
    .st-n-btn svg { width: 11px; height: 11px; stroke: currentColor; }
    .st-n-btn:hover { background: rgba(155,93,229,.1); }
    .st-n-val { font-size: 0.75rem; font-weight: 700; color: var(--text); min-width: 14px; text-align: center; }
    .st-n-label { font-size: 0.68rem; color: var(--text-3); flex: 1; }
    #stereo-unfold-btn.active, #stereo-measure-btn.active,
    #stereo-point-btn.active, #stereo-connect-btn.active,
    #stereo-mark-tick-btn.active, #stereo-mark-par-btn.active,
    #stereo-derive-mid-btn.active, #stereo-derive-fc-btn.active, #stereo-derive-alt-btn.active, #stereo-derive-cen-btn.active,
    #stereo-angle-edge-btn.active, #stereo-angle-lp-btn.active, #stereo-angle-dih-btn.active, #stereo-angle-pp-btn.active, #stereo-angle-skew-btn.active {
      border-color: var(--violet) !important; color: var(--violet) !important; background: rgba(155,93,229,.12) !important;
    }

    .gp-preset-group { margin-bottom: 8px; }
    .gp-preset-label {
      font-size: 0.68rem; font-weight: 700; text-transform: uppercase;
      letter-spacing: .06em; color: var(--text-3);
      margin: 6px 0 4px;
    }

    /* canvas area */
    .graph-canvas-outer {
      flex: 1; min-width: 0; min-height: 0;
      display: flex; flex-direction: column;
    }
    .graph-canvas-wrap {
      flex: 1; min-height: 0; position: relative;
    }
    #graph-canvas { display: block; position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

    /* info bar */
    .graph-info-bar {
      flex-shrink: 0;
      display: flex; align-items: center; gap: 20px;
      padding: 8px 18px;
      background: #0D0D1A;
      border-top: 1px solid rgba(255,255,255,.07);
      font-family: 'Manrope', monospace; font-size: 0.8rem;
      color: rgba(255,255,255,.4);
      min-height: 36px;
    }
    .info-coord { display: flex; align-items: center; gap: 6px; }
    .info-coord .ic-label { color: rgba(255,255,255,.25); }
    .info-coord .ic-val { color: rgba(255,255,255,.7); font-weight: 700; min-width: 52px; }
    .info-fn-val { display: flex; align-items: center; gap: 6px; }
    .info-fn-dot { width: 8px; height: 8px; border-radius: 50%; flex-shrink: 0; }
    .info-fn-val .ic-val { color: rgba(255,255,255,.7); font-weight: 700; min-width: 60px; }
    .info-hint { margin-left: auto; font-size: 0.72rem; color: rgba(255,255,255,.2); }

    /* ════════════════════════════════
       PROJECTILE SIM
    ════════════════════════════════ */
    .sim-proj-wrap {
      flex: 1; min-height: 0;
      display: flex; flex-direction: column; overflow: hidden;
    }

    /* left panel (shared base with .graph-panel) */
    .proj-panel {
      width: 260px; flex-shrink: 0;
      background: var(--surface);
      border-right: 1.5px solid var(--border);
      display: flex; flex-direction: column;
      overflow-y: auto; padding: 16px 14px; gap: 6px;
    }

    /* canvas */
    .proj-canvas-outer {
      flex: 1; min-width: 0; position: relative;
    }
    .proj-canvas-outer canvas {
      display: block; position: absolute; top: 0; left: 0;
      width: 100%; height: 100%;
    }

    /* sliders */
    .param-block  { display: flex; flex-direction: column; gap: 4px; margin-bottom: 10px; }
    .param-header { display: flex; justify-content: space-between; align-items: baseline; }
    .param-name   { font-size: 0.8rem; font-weight: 700; color: var(--text-2); }
    .param-val    {
      font-family: 'Manrope', monospace; font-size: 0.82rem; font-weight: 800;
      color: var(--violet); min-width: 70px; text-align: right;
    }
    .param-slider {
      -webkit-appearance: none; appearance: none;
      width: 100%; height: 4px; border-radius: 4px;
      background: var(--border-h); outline: none; cursor: pointer;
    }
    .param-slider::-webkit-slider-thumb {
      -webkit-appearance: none; width: 16px; height: 16px; border-radius: 50%;
      background: var(--violet); box-shadow: 0 0 6px rgba(155,93,229,.5);
      cursor: pointer;
    }
    .param-slider::-moz-range-thumb {
      width: 16px; height: 16px; border-radius: 50%; border: none;
      background: var(--violet); cursor: pointer;
    }

    /* preset chips for projectile */
    .proj-preset-chip {
      padding: 5px 10px; border-radius: 8px; font-size: 0.75rem; font-weight: 700;
      border: 1.5px solid var(--border-h); background: transparent;
      color: var(--text-2); cursor: pointer; transition: all .15s; white-space: nowrap;
    }
    .proj-preset-chip:hover { border-color: var(--violet); color: var(--violet); background: rgba(155,93,229,.06); }

    /* stats bar */
    .proj-stats-bar {
      flex-shrink: 0; display: flex; align-items: stretch;
      background: #0D0D1A; border-top: 1px solid rgba(255,255,255,.07);
      min-height: 48px;
    }
    .pstat {
      flex: 1; display: flex; flex-direction: column;
      align-items: center; justify-content: center;
      gap: 2px; padding: 6px 8px;
      border-right: 1px solid rgba(255,255,255,.06);
    }
    .pstat:last-child { border-right: none; }
    .pstat-label { font-size: 0.62rem; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; color: rgba(255,255,255,.3); }
    .pstat-val   { font-family: 'Manrope', monospace; font-size: 0.9rem; font-weight: 800; color: rgba(255,255,255,.85); }
    #csbar-v4, #csbar-v6 { font-size: 0.60rem; max-width: 180px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

    /* play button highlight */
    .zoom-btn.active { border-color: var(--violet); color: var(--violet); background: rgba(155,93,229,.12); }

    /* ── launch button ── */
    .proj-launch-btn {
      width: 100%; padding: 14px 18px;
      border-radius: 16px; border: none;
      background: linear-gradient(135deg, #7c3aed 0%, #9B5DE5 45%, #F15BB5 100%);
      color: #fff;
      font-family: 'Unbounded', sans-serif; font-size: 0.8rem; font-weight: 800;
      letter-spacing: .04em; text-transform: uppercase;
      cursor: pointer;
      display: flex; align-items: center; justify-content: center; gap: 10px;
      box-shadow: 0 4px 24px rgba(155,93,229,.45), 0 0 0 0 rgba(155,93,229,.3);
      transition: transform .15s, box-shadow .15s;
      position: relative; overflow: hidden;
    }
    .proj-launch-btn::before {
      content: ''; position: absolute; inset: 0;
      background: linear-gradient(135deg, rgba(255,255,255,.15) 0%, transparent 60%);
      pointer-events: none;
    }
    .proj-launch-btn:hover {
      transform: translateY(-2px);
      box-shadow: 0 8px 32px rgba(155,93,229,.6), 0 0 0 3px rgba(155,93,229,.15);
    }
    .proj-launch-btn:active { transform: translateY(0); }
    .proj-launch-btn.paused {
      background: linear-gradient(135deg, #0891b2 0%, #06D6E0 100%);
      box-shadow: 0 4px 24px rgba(6,214,224,.35);
    }
    .proj-launch-btn.done {
      background: linear-gradient(135deg, #15803d 0%, #22c55e 100%);
      box-shadow: 0 4px 24px rgba(34,197,94,.35);
    }
    .proj-reset-btn {
      width: 100%; padding: 8px;
      border-radius: 10px;
      border: 1.5px solid var(--border-h);
      background: transparent; color: var(--text-3);
      font-family: 'Manrope', sans-serif; font-size: 0.75rem; font-weight: 700;
      cursor: pointer; transition: all .15s;
      display: flex; align-items: center; justify-content: center; gap: 7px;
    }
    .proj-reset-btn:hover { border-color: var(--violet); color: var(--violet); }

    /* speed slider — cyan thumb */
    #sl-speed::-webkit-slider-thumb {
      background: var(--cyan);
      box-shadow: 0 0 6px rgba(6,214,224,.5);
    }
    #sl-speed::-moz-range-thumb { background: var(--cyan); }

    /* graphs panel canvas (Feature 2) */
    .proj-graphs-canvas {
      display: block; width: 100%; height: 200px;
    }

    /* dual-throw slider — cyan thumb */
    .proj-dual-slider::-webkit-slider-thumb {
      background: #00E6FF;
      box-shadow: 0 0 6px rgba(0,230,255,.5);
    }
    .proj-dual-slider::-moz-range-thumb { background: #00E6FF; }

    /* magnetic canvas */
    #mag-canvas {
      display: block; position: absolute; top: 0; left: 0; width: 100%; height: 100%;
      cursor: crosshair;
    }

    /* mode buttons */
    .mag-mode-btn {
      flex: 1; padding: 8px 6px; border-radius: 10px;
      border: 1.5px solid var(--border-h);
      background: transparent; color: var(--text-2);
      font-family: 'Manrope', sans-serif; font-size: 0.75rem; font-weight: 700;
      cursor: pointer; transition: all .15s;
      display: flex; align-items: center; justify-content: center; gap: 6px;
    }
    .mag-mode-btn:hover { border-color: var(--violet); color: var(--text); }
    .mag-mode-btn.active {
      background: rgba(155,93,229,.15); border-color: var(--violet); color: #fff;
    }

    /* triangle canvas */
    #tri-canvas {
      display: block; position: absolute; top: 0; left: 0; width: 100%; height: 100%;
    }

    /* molecular physics canvases */
    #gas-canvas, #brownian-canvas, #states-canvas, #diffusion-canvas, #reactions-canvas {
      display: block; position: absolute; top: 0; left: 0; width: 100%; height: 100%;
    }

    /* chemistry sim-cat badge */
    .sim-cat.chem { background: rgba(52,211,153,.1); color: #34d399; }
    /* biology sim-cat badge */
    .sim-cat.bio  { background: rgba(34,211,153,.1); color: #22d399; }
    /* phase dot navigator */
    .cd-phase-nav { display:flex; align-items:center; justify-content:center; gap:6px; padding:6px 0; flex-wrap:wrap; }
    .cd-phase-dot { width:8px; height:8px; border-radius:50%; background:var(--border-h,rgba(255,255,255,.15)); cursor:pointer; transition:background .2s,transform .2s; flex-shrink:0; }
    .cd-phase-dot.active { background:#22d399; transform:scale(1.5); }

    /* ── triangle panel components ── */
    .tri-layer-row {
      display: flex; align-items: center; gap: 8px;
      padding: 7px 10px; border-radius: 10px;
      border: 1.5px solid var(--border);
      background: rgba(15,23,42,.03);
      cursor: pointer; user-select: none;
      transition: border-color .15s, background .15s;
    }
    .tri-layer-row:hover { background: rgba(155,93,229,.05); border-color: rgba(155,93,229,.3); }
    .tri-layer-row.active { background: rgba(155,93,229,.08); border-color: rgba(155,93,229,.4); }

    .tri-dot {
      width: 9px; height: 9px; border-radius: 50%; flex-shrink: 0;
    }
    .tri-layer-name {
      font-size: 0.78rem; font-weight: 700; color: var(--text); flex: 1;
    }
    .tri-layer-hint {
      font-size: 0.68rem; font-weight: 700; opacity: 0.8;
    }
    .tri-toggle {
      width: 28px; height: 16px; border-radius: 99px;
      background: var(--border-h); flex-shrink: 0;
      position: relative; transition: background .2s;
    }
    .tri-toggle::after {
      content: ''; position: absolute; top: 2px; left: 2px;
      width: 12px; height: 12px; border-radius: 50%;
      background: #fff; transition: transform .2s;
    }
    .tri-layer-row.active .tri-toggle { background: var(--violet); }
    .tri-layer-row.active .tri-toggle::after { transform: translateX(12px); }

    .tri-stats-grid {
      display: grid; grid-template-columns: 26px 1fr; gap: 3px 8px;
      padding: 0 4px;
    }
    .tri-stat-k {
      font-family: 'Manrope', monospace; font-size: 0.78rem; font-weight: 800;
      display: flex; align-items: center;
    }
    .tri-stat-v {
      font-family: 'Manrope', monospace; font-size: 0.82rem; font-weight: 700;
      color: var(--text); padding: 2px 6px;
      border-radius: 6px; background: rgba(15,23,42,.08);
    }

    /* ── trig circle buttons ── */
    .trig-fn-btn {
      padding: 6px 14px; border-radius: 8px;
      background: rgba(255,255,255,0.05); border: 1px solid rgba(255,255,255,0.10);
      color: #aaa; font-size: 13px; font-weight: 700; cursor: pointer;
      font-family: 'Manrope', sans-serif; transition: .15s;
    }
    .trig-fn-btn:hover { background: rgba(var(--fc-rgb,155,93,229),0.15); border-color: var(--fc,var(--violet)); color: var(--fc,var(--violet)); }
    .trig-fn-btn.active { background: rgba(var(--fc-rgb,155,93,229),0.18); border-color: var(--fc,var(--violet)); color: var(--fc,var(--violet)); box-shadow: 0 0 8px rgba(var(--fc-rgb,155,93,229),0.3); }

    /* ── responsive ── */
    @media (max-width: 768px) {
      #lab-home { padding: 20px 16px 60px; }
      .sim-grid { grid-template-columns: 1fr 1fr; gap: 14px; }
      .graph-panel { width: 220px; }
      /* Touch-friendly button targets (min 44px) */
      .zoom-btn { width: auto; min-width: 44px; height: 44px; padding: 0 12px; border-radius: 12px; }
      .sim-back { padding: 10px 16px; min-height: 44px; }
      .theory-toggle-btn { width: 44px; height: 44px; border-radius: 12px; }
    }
    @media (max-width: 540px) {
      .sim-grid { grid-template-columns: 1fr; }
      .sim-body-wrap { flex-direction: column; }
      .graph-panel { width: 100%; height: auto; border-right: none; border-bottom: 1.5px solid var(--border); max-height: 220px; }
    }

  /* Circuit tool buttons */
  .circ-tool-btn.active {
    background: rgba(155,93,229,0.25) !important;
    border-color: var(--violet) !important;
    color: #c4b5fd !important;
  }
  .circ-top-btn.active { background: rgba(155,93,229,0.35) !important; color: #c4b5fd !important; }

  /* Flask selection buttons */
  .flask-metal-btn.active, .flask-acid-btn.active {
    background: rgba(75,205,155,0.20) !important;
    border-color: #4BCD9B !important;
    color: #7BF5A4 !important;
  }

  /* Reaction mode buttons */
  .reac-mode-btn.active {
    background: rgba(6,214,224,0.18) !important;
    border-color: var(--cyan) !important;
    color: var(--cyan) !important;
  }

  /* Newton law/scene buttons */
  .nlaw-btn.active {
    background: rgba(6,214,224,0.18) !important;
    border-color: var(--cyan) !important;
    color: var(--cyan) !important;
  }
  .nscene-btn.active {
    background: rgba(241,91,181,0.15) !important;
    border-color: var(--pink) !important;
    color: var(--pink) !important;
  }

  /* ── wave mode buttons ── */
  .wave-mode-btn {
    flex: 1; padding: 7px 4px; border-radius: 10px;
    border: 1.5px solid var(--border-h);
    background: transparent; color: var(--text-2);
    font-family: 'Manrope', sans-serif; font-size: 0.72rem; font-weight: 700;
    cursor: pointer; transition: all .15s; text-align: center;
  }
  .wave-mode-btn:hover { border-color: var(--violet); color: var(--text); }
  .wave-mode-btn.active {
    background: rgba(155,93,229,.15) !important;
    border-color: var(--violet) !important; color: #fff !important;
  }
  .wave-n-btn.active {
    background: rgba(255,209,102,.15) !important;
    border-color: #FFD166 !important; color: #FFD166 !important; /* amber — wave harmonic, intentional palette */
  }

  /* ── theory panel (overlay right sidebar) ── */
  #lab-sim { position: relative; }
  .theory-panel {
    position: absolute; right: 0; top: 0; bottom: 0; z-index: 55;
    width: 320px;
    background: var(--surface);
    border-left: 1.5px solid var(--border);
    transform: translateX(100%);
    transition: transform 0.25s cubic-bezier(.4,0,.2,1);
    display: flex; flex-direction: column;
    box-shadow: -4px 0 24px rgba(0,0,0,0.12);
  }
  .theory-panel.open { transform: translateX(0); }
  .theory-panel-inner {
    padding: 20px 16px; overflow-y: auto; flex: 1;
    display: flex; flex-direction: column; gap: 16px;
  }
  .tp-title {
    font-family: 'Unbounded', sans-serif; font-size: 0.72rem; font-weight: 800;
    color: var(--text-3); text-transform: uppercase; letter-spacing: .06em;
    display: flex; align-items: center; gap: 8px;
  }
  .tp-title::after { content: ''; flex: 1; height: 1px; background: var(--border); }
  .tp-section { margin-bottom: 4px; }
  .tp-section-head {
    font-size: 0.76rem; font-weight: 800; color: var(--violet);
    margin-bottom: 6px; display: flex; align-items: center; gap: 6px;
  }
  .tp-formula {
    background: rgba(155,93,229,0.06); border: 1px solid rgba(155,93,229,0.12);
    border-radius: 10px; padding: 10px 12px; margin-bottom: 8px;
    font-size: 0.88rem; text-align: center;
  }
  .tp-formula .katex { font-size: 1em; }
  .tp-text {
    font-size: 0.78rem; color: var(--text-2); line-height: 1.6; margin-bottom: 8px;
  }
  .tp-var-list { display: flex; flex-direction: column; gap: 3px; margin-bottom: 8px; }
  .tp-var {
    font-size: 0.74rem; color: var(--text-2); display: flex; gap: 6px;
    padding: 3px 0; border-bottom: 1px dashed rgba(255,255,255,0.04);
  }
  .tp-var b { color: var(--text); font-weight: 700; min-width: 24px; }
  .theory-toggle-btn {
    position: absolute; right: 8px; top: 50%; transform: translateY(-50%);
    width: 32px; height: 32px; border-radius: 10px;
    border: 1.5px solid var(--border-h); background: transparent; color: var(--text-2);
    cursor: pointer; display: flex; align-items: center; justify-content: center;
    transition: all 0.15s; z-index: 2;
  }
  .theory-toggle-btn:hover { border-color: var(--violet); color: var(--violet); background: rgba(155,93,229,0.07); }
  .theory-toggle-btn svg { width: 15px; height: 15px; stroke: currentColor; stroke-width: 2.2; }
  @media (max-width: 768px) {
    .theory-panel.open { width: 100%; position: absolute; right: 0; top: 0; bottom: 0; z-index: 60; }
  }

  /* ── embed mode (loaded in iframe, no sidebar/topbar) ── */
  .embed-mode { height: 100vh; }
  .embed-mode .sb-content { height: 100vh; margin-left: 0 !important; }
  .embed-mode #lab-sim { flex: 1; }
  .embed-mode .sim-body-wrap { height: 100vh; }
  .embed-mode .graph-panel { max-height: 100vh; }

  /* ════════════════════════════════
     GEOMETRY SIM STYLES
  ════════════════════════════════ */
  .geo-panel {
    width: 210px; flex-shrink: 0;
    background: var(--surface);
    border-right: 1.5px solid var(--border);
    display: flex; flex-direction: column;
    overflow-y: auto; padding: 12px 10px; gap: 4px;
  }
  .geo-tool-grid {
    display: grid; grid-template-columns: 1fr 1fr; gap: 4px;
    margin-bottom: 4px;
  }
  .geo-tool-btn {
    display: flex; align-items: center; gap: 6px;
    padding: 7px 9px; border-radius: 10px;
    border: 1.5px solid var(--border);
    background: transparent; color: var(--text-2);
    font-family: 'Manrope', sans-serif; font-size: 0.73rem; font-weight: 700;
    cursor: pointer; transition: all .14s; white-space: nowrap;
  }
  .geo-tool-btn svg { width: 13px; height: 13px; stroke: currentColor; stroke-width: 2.2; flex-shrink: 0; }
  .geo-tool-btn:hover { border-color: rgba(155,93,229,.4); color: var(--violet); background: rgba(155,93,229,.06); }
  .geo-tool-btn.active { border-color: var(--violet); color: var(--violet); background: rgba(155,93,229,.12); }

  .geo-tool-wide {
    grid-column: span 2;
  }

  .geo-ngon-ctrl {
    display: flex; align-items: center; justify-content: center; gap: 6px;
    border: 1.5px solid var(--border); border-radius: 10px;
    padding: 4px 6px;
  }
  .geo-ngon-btn {
    width: 22px; height: 22px; border-radius: 6px;
    border: 1px solid var(--border-h);
    background: transparent; color: var(--text-2);
    cursor: pointer; display: flex; align-items: center; justify-content: center;
    transition: background .12s;
  }
  .geo-ngon-btn svg { width: 12px; height: 12px; stroke: currentColor; }
  .geo-ngon-btn:hover { background: rgba(155,93,229,.1); }
  #geo-ngon-n {
    font-size: 0.78rem; font-weight: 700; color: var(--text);
    min-width: 18px; text-align: center;
  }

  .geo-toggle-row {
    display: flex; align-items: center; justify-content: space-between;
    padding: 5px 4px; border-radius: 8px; cursor: pointer;
    transition: background .13s;
  }
  .geo-toggle-row:hover { background: rgba(255,255,255,.04); }
  .geo-toggle-label {
    font-size: 0.73rem; font-weight: 600; color: var(--text-2);
    display: flex; align-items: center; gap: 6px;
  }
  .geo-toggle-label svg { width: 12px; height: 12px; stroke: currentColor; stroke-width: 2; opacity: .7; }
  .geo-toggle {
    width: 28px; height: 16px; border-radius: 8px;
    background: rgba(255,255,255,.1); border: 1.5px solid var(--border-h);
    position: relative; transition: background .15s; flex-shrink: 0;
  }
  .geo-toggle::after {
    content: ''; position: absolute; left: 2px; top: 50%;
    transform: translateY(-50%);
    width: 9px; height: 9px; border-radius: 50%;
    background: rgba(255,255,255,.4); transition: all .15s;
  }
  .geo-toggle.on { background: var(--violet); border-color: var(--violet); }
  .geo-toggle.on::after { left: calc(100% - 11px); background: #fff; }

  .geo-info-box {
    background: rgba(155,93,229,.07); border: 1px solid rgba(155,93,229,.15);
    border-radius: 10px; padding: 8px 10px; margin-top: 4px;
    font-size: 0.72rem; line-height: 1.55; color: var(--text-2);
  }
  .geo-info-box .geo-info-key { color: var(--violet); font-weight: 700; }

  .geo-stat-row {
    display: flex; justify-content: space-between; align-items: center;
    font-size: 0.7rem; padding: 2px 0;
    border-bottom: 1px dashed rgba(255,255,255,.05);
    color: var(--text-2);
  }
  .geo-stat-row:last-child { border: none; }
  .geo-stat-row b { color: var(--text); font-weight: 700; }

  .geo-canvas-outer {
    flex: 1; min-width: 0; position: relative; background: #0a0718;
  }
  .geo-canvas-outer canvas {
    display: block; position: absolute; top: 0; left: 0;
    width: 100%; height: 100%;
  }

  .geo-hint-bar {
    position: absolute; bottom: 8px; left: 50%; transform: translateX(-50%);
    background: rgba(10,7,24,.82); border: 1px solid rgba(255,255,255,.1);
    border-radius: 20px; padding: 4px 14px;
    font-size: 0.7rem; color: rgba(255,255,255,.5);
    pointer-events: none; white-space: nowrap;
    backdrop-filter: blur(6px);
  }
  .geo-del-confirm {
    display: none; position: absolute; top: 8px; left: 50%; transform: translateX(-50%);
    gap: 8px; align-items: center; white-space: nowrap;
    background: rgba(18,10,32,.96); border: 1px solid rgba(155,93,229,.35);
    border-radius: 10px; padding: 8px 12px; z-index: 20;
    backdrop-filter: blur(8px); box-shadow: 0 4px 20px rgba(0,0,0,.6);
    font-size: 0.72rem; color: rgba(255,255,255,.8);
  }
  .geo-del-confirm.visible { display: flex; }
  .geo-del-confirm span { margin-right: 2px; }
  .geo-del-btn {
    padding: 3px 9px; border-radius: 6px; border: 1px solid;
    font-size: 0.7rem; cursor: pointer; font-family: inherit;
    transition: background .15s;
  }
  .geo-del-btn-soft  { border-color: rgba(74,222,128,.4); color: #4ADE80; background: rgba(74,222,128,.08); }
  .geo-del-btn-soft:hover  { background: rgba(74,222,128,.18); }
  .geo-del-btn-hard  { border-color: rgba(248,113,113,.4); color: #f87171; background: rgba(248,113,113,.08); }
  .geo-del-btn-hard:hover  { background: rgba(248,113,113,.18); }
  .geo-del-btn-cancel{ border-color: rgba(255,255,255,.15); color: rgba(255,255,255,.5); background: transparent; }
  .geo-del-btn-cancel:hover{ background: rgba(255,255,255,.06); }