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.btn-primary:hover:not(:disabled){background:#2b2f4c}.read-foot .btn-primary svg{transition:transform var(--t-fast) var(--ease)}.read-foot .btn-primary:hover svg{transform:translate(3px)}.btn.jump-exp,.icon-btn.jump-read{display:none}.btn{border-radius:var(--r-pill);white-space:nowrap;min-height:46px;transition:background var(--t-fast), border-color var(--t-fast), box-shadow var(--t-fast), transform var(--t-fast);border:1px solid #0000;justify-content:center;align-items:center;gap:8px;padding:0 20px;font-size:1rem;font-weight:700;line-height:1.1;text-decoration:none;display:inline-flex}.btn:active:not(:disabled){transform:translateY(1px)}.btn:disabled{opacity:.4}.btn-primary{background:var(--accent);color:#fff;box-shadow:var(--shadow-accent)}.btn-primary:hover:not(:disabled){background:var(--accent-strong)}.btn-primary:disabled{box-shadow:none}.btn-ghost{background:var(--surface);border-color:var(--line-2);color:var(--ink)}.btn-ghost:hover:not(:disabled){background:var(--surface-2);border-color:#c4c6d8}.btn-tutor{background:var(--ink);color:#fff}.btn-tutor:hover{background:#2b2f4c}.btn-tutor[aria-expanded=true]{background:var(--accent)}.btn-small{min-height:42px;font-size:var(--text-s);padding:0 16px}.btn-icon{width:46px;padding:0}.btn-hold{touch-action:none;-webkit-user-select:none;user-select:none;-webkit-touch-callout:none;min-width:168px;min-height:58px;box-shadow:var(--shadow-accent), inset 0 -3px 0 #00000029;padding:0 28px;font-size:1.1rem;font-weight:750;position:relative}.btn-hold:active:not(:disabled),.btn-hold[data-holding]{background:var(--accent-strong);transform:translateY(2px)scale(.97);box-shadow:0 4px 10px -6px #4338cacc,inset 0 2px #0000002e}.btn-hold[data-holding]:after{content:"";border-radius:inherit;pointer-events:none;border:3px solid #6366f173;animation:1s ease-out infinite hold-ring;position:absolute;inset:-6px}@keyframes hold-ring{0%{opacity:1;transform:scale(.96)}to{opacity:0;transform:scale(1.12)}}.icon-btn{border:1px solid var(--line-2);background:var(--surface);width:38px;height:38px;color:var(--ink);transition:background var(--t-fast), border-color var(--t-fast), transform var(--t-med) var(--ease);border-radius:12px;flex-shrink:0;place-items:center;display:inline-grid}.icon-btn-lg{border-radius:15px;width:46px;height:46px}.icon-btn:hover:not(:disabled){background:var(--surface-2);border-color:#c4c6d8}.icon-btn:disabled{opacity:.35}.exp-dock .icon-btn-lg{border-radius:50%;width:52px;height:52px}.exp-dock .icon-btn-lg[aria-label=Reset]:hover:not(:disabled){transform:rotate(-45deg)}.link-btn{color:var(--accent-strong);text-underline-offset:4px;text-align:left;transition:text-decoration-color var(--t-fast);background:0 0;border:0;align-items:center;gap:5px;padding:2px 0;font-size:1rem;font-weight:700;-webkit-text-decoration:underline #3730a359;text-decoration:underline #3730a359;text-decoration-thickness:1.5px;display:inline-flex}.link-btn:hover{text-decoration-color:currentColor}.segmented{background:var(--surface-3);border-radius:17px;gap:4px;padding:5px;display:inline-flex}.segmented-opt{min-height:44px;color:var(--ink-2);transition:background var(--t-fast), color var(--t-fast), box-shadow var(--t-fast);background:0 0;border:0;border-radius:13px;align-items:center;gap:8px;padding:0 18px 0 14px;font-size:1rem;font-weight:700;display:inline-flex}.segmented-opt:hover{color:var(--ink)}.segmented-opt[aria-checked=true]{background:var(--surface);color:var(--ink);box-shadow:0 1px 2px #171a2f14,0 6px 14px -8px #171a2f59}.qslider{--q:var(--accent);--q-soft:var(--accent-soft);border-radius:var(--r-l);background:var(--surface-2);flex:1;min-width:200px;padding:12px 16px 8px}.qslider[data-q=force]{--q:var(--force);--q-soft:var(--force-soft)}.qslider[data-q=disp]{--q:var(--disp);--q-soft:var(--disp-soft)}.qslider[data-q=dist]{--q:var(--dist);--q-soft:var(--dist-soft)}.qslider[data-q=vel]{--q:var(--vel);--q-soft:var(--vel-soft)}.qslider[data-q=acc]{--q:var(--acc);--q-soft:var(--acc-soft)}.qslider[data-q=time]{--q:var(--ink-2);--q-soft:var(--surface-3)}.qslider[data-disabled]{opacity:.55}.qslider-top{justify-content:space-between;align-items:baseline;gap:8px;display:flex}.qslider-label{font-weight:700;font-size:var(--text-s);color:var(--ink-2)}.qslider-symbol{font-family:var(--font-display);color:var(--q);font-style:italic;font-weight:750}.qslider-value{font-family:var(--font-display);letter-spacing:-.01em;color:var(--q);font-size:1.45rem;font-weight:700}.qslider input[type=range]{appearance:none;cursor:pointer;background:0 0;width:100%;height:34px;margin:0}.qslider input[type=range]:disabled{cursor:not-allowed}.qslider input[type=range]::-webkit-slider-runnable-track{border-radius:var(--r-pill);background:linear-gradient(to right, var(--q) 0 var(--pct), #fff var(--pct) 100%);height:8px;box-shadow:inset 0 0 0 1px var(--line-2)}.qslider input[type=range]::-moz-range-track{border-radius:var(--r-pill);height:8px;box-shadow:inset 0 0 0 1px var(--line-2);background:#fff}.qslider input[type=range]::-moz-range-progress{border-radius:var(--r-pill);background:var(--q);height:8px}.qslider input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;border:4px solid var(--q);width:26px;height:26px;transition:transform var(--t-fast);background:#fff;border-radius:50%;margin-top:-9px;box-shadow:0 4px 10px -3px #171a2f59}.qslider input[type=range]:active::-webkit-slider-thumb{transform:scale(1.12)}.qslider input[type=range]::-moz-range-thumb{border:4px solid var(--q);background:#fff;border-radius:50%;width:18px;height:18px}.qslider input[type=range]:focus-visible{outline:3px solid var(--focus);outline-offset:4px}.unit{opacity:.85;letter-spacing:0;font-size:.72em;font-weight:650}.readouts{grid-template-columns:repeat(auto-fit,minmax(min(140px,100%),1fr));gap:10px;display:grid}.readout{--q:var(--ink);--q-bg:var(--surface-2);border-radius:var(--r-l);background:var(--q-bg);flex-direction:column;gap:2px;min-width:0;padding:12px 16px 14px;display:flex}.readout[data-q=force]{--q:var(--force)}.readout[data-q=disp]{--q:var(--disp)}.readout[data-q=work]{--q:var(--work);--q-bg:var(--work-soft)}.readout[data-q=dist]{--q:var(--dist)}.readout[data-q=vel]{--q:var(--vel)}.readout[data-q=acc]{--q:var(--acc)}.readout[data-q=time]{--q:var(--ink-2)}.dock-row>.readout{flex:220px}.readout-label{font-size:var(--text-xs);color:var(--ink-2);font-weight:700}.readout-value{font-family:var(--font-display);letter-spacing:-.02em;color:var(--q);font-size:1.85rem;font-weight:700;line-height:1.15}.readout[data-big] .readout-value{font-size:2.2rem}.readout-note{font-size:var(--text-xs);color:var(--ink-2)}.exp{flex-direction:column;display:flex;position:relative;overflow:hidden}.exp:focus{outline:none}.exp[data-expanded]{z-index:60;box-shadow:none;padding:env(safe-area-inset-top) env(safe-area-inset-right) max(12px, env(safe-area-inset-bottom)) env(safe-area-inset-left);border:0;border-radius:0;animation:.2s ease-out exp-expand;position:fixed;inset:0}@keyframes exp-expand{0%{opacity:0;transform:scale(.985)}}.exp[data-expanded]>*{width:100%;max-width:1680px;margin-inline:auto}.exp[data-expanded] .jump-read{display:none}.exp[data-expanded] .exp-stage{aspect-ratio:auto;flex:auto;min-height:0;max-height:none}.exp-expand[aria-label^=Exit]{background:var(--ink);border-color:var(--ink);color:#fff}.exp-expand[aria-label^=Exit]:hover:not(:disabled){background:#2b2f4d;border-color:#2b2f4d}body[data-exp-expanded] .tutor{z-index:70;width:min(390px,100vw - 40px);box-shadow:var(--shadow-3);position:fixed;top:20px;bottom:20px;right:20px}@media (prefers-reduced-motion:reduce){.exp[data-expanded]{animation:none}}.exp-head{flex-shrink:0;justify-content:space-between;align-items:center;gap:12px;padding:14px 16px 12px 22px;display:flex}.exp-title{align-items:center;gap:12px;min-width:0;display:flex}.exp-title>div{min-width:0}.exp-badge{background:var(--accent-soft);width:36px;height:36px;color:var(--accent);border-radius:11px;flex-shrink:0;place-items:center;display:grid}.exp-kicker{font-size:var(--text-xs);letter-spacing:.07em;text-transform:uppercase;color:var(--ink-3);font-weight:750;line-height:1.2;display:block}.exp-title h2{letter-spacing:-.01em;white-space:nowrap;text-overflow:ellipsis;font-size:1.12rem;font-weight:700;line-height:1.25;overflow:hidden}.exp-corner{flex-shrink:0;align-items:center;gap:8px;display:flex}.about{position:relative}.about-btn[aria-expanded=true]{background:var(--accent-soft);color:var(--accent-strong);border-color:#c9c5fb}.about-card{z-index:10;border-radius:var(--r-l);background:var(--surface);border:1px solid var(--line);width:min(340px,82vw);box-shadow:var(--shadow-3);font-size:var(--text-s);animation:fade-up .22s var(--ease) both;padding:16px 18px;line-height:1.5;position:absolute;top:46px;right:0}.about-card[hidden]{display:none}.about-title{margin-bottom:6px;font-weight:750}.about-card ul{margin:0;padding-left:18px}.about-card li+li{margin-top:6px}.exp-stage{isolation:isolate;background:#ece9fb;border-radius:22px;flex:1;min-height:240px;margin:0 12px;position:relative;overflow:hidden;box-shadow:inset 0 0 0 1px #171a2f0d}.exp-stage[data-scene=outdoor]{background:#dfe6ff}.exp-stage[data-scene=grid]{background:#fbfaff}.exp-stage[data-scene=lab]{background:#f3f0fc}.scene-svg{-webkit-user-select:none;user-select:none;width:100%;height:100%;display:block;position:absolute;inset:0}.svg-label{font-family:var(--font-body);paint-order:stroke;stroke:#ffffffeb;stroke-width:5px;stroke-linejoin:round;font-weight:700}.scene-svg text{font-family:var(--font-body)}.graph-svg{width:100%;height:100%;font-family:var(--font-body);display:block}.graph-stage{flex-direction:column;display:flex}.graph-stage-strip{border-bottom:1px solid var(--line);flex:0 0 32%;min-height:112px;max-height:190px;position:relative}.graph-stage-plot{flex:1;min-height:170px;padding:6px 8px 2px}.graph-figure{border-radius:var(--r-m);background:var(--surface-2);height:230px;margin:2px 0 16px;padding:6px}.drag-handle{cursor:grab;touch-action:none}.drag-handle:active{cursor:grabbing}.flag[data-active] path{filter:drop-shadow(0 2px 3px #171a2f40)}.emph{animation:emph 1.6s var(--ease) infinite}@keyframes emph{50%{opacity:.45}}.pulse-outline{animation:1.2s linear infinite dash}@keyframes dash{to{stroke-dashoffset:-24px}}.pop-in{animation:pop .42s var(--ease) both;transform-box:fill-box;transform-origin:50%}@keyframes pop{0%{opacity:0;transform:scale(.85)}}.sweat{animation:1.2s ease-in-out infinite sweat}@keyframes sweat{50%{opacity:.6;transform:translateY(4px)}}.strain-lines{animation:.5s linear infinite emph}.tile{fill:#f1eefc;transition:fill .22s var(--ease)}.tile[data-filled]{fill:var(--work-tile);stroke:#a998f0;stroke-width:1.5px}.tile-outline{transition:all .22s var(--ease)}.joule-scene text{font-variant-numeric:tabular-nums}.joule-tile{fill:#efedf9;transform-box:fill-box;transform-origin:50%;transition:fill .26s var(--ease), transform .36s var(--ease);transform:scale(.82)}.joule-tile[data-filled]{fill:#cfc3fb;transform:scale(1)}.joule-area{transition:x .3s var(--ease), y .3s var(--ease), width .3s var(--ease), height .3s var(--ease);filter:drop-shadow(0 4px 10px #5b3fd02e)}.joule-crate,.joule-handle{transition:transform .3s var(--ease)}.joule-handle{pointer-events:none}.joule-hit{cursor:crosshair;touch-action:none}.joule-total{transform-box:fill-box;transform-origin:0;animation:pop .36s var(--ease) both}.joule-fade{animation:fade-up .24s var(--ease) both}.exp-dock{flex-direction:column;flex-shrink:0;gap:14px;padding:16px 20px 20px;display:flex}.dock-row{flex-wrap:wrap;justify-content:space-between;align-items:center;gap:12px 18px;display:flex}.dock-row-start{justify-content:flex-start}.dock-row-sliders{grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:10px;display:grid}.dock-actions{flex-wrap:wrap;align-items:center;gap:10px;display:flex}.readouts-inline{flex:300px}.gap-table{border-collapse:separate;border-spacing:4px;font-size:var(--text-s);flex:320px}.gap-table th{color:var(--ink-2);text-align:left;padding:2px 6px;font-weight:700}.gap-table thead th{font-size:var(--text-xs);text-align:center}.gap-table thead th:first-child{text-align:left}.gap-table td{border-radius:var(--r-xs);background:var(--surface-2);text-align:center;min-width:44px;padding:6px 4px;font-weight:700}.gap-table tr[data-racer=car] td{color:var(--force)}.gap-table tr[data-racer=auto] td{color:var(--dist)}.readout-direction{align-items:center;font-size:1.3rem;display:inline-flex}.dock-row-three{grid-template-columns:repeat(auto-fit,minmax(170px,1fr))}.dock-given{font-size:var(--text-m);color:var(--ink-2);margin:0;font-weight:600}.readings-table td[data-plotted]{background:var(--disp-soft);color:var(--disp)}.calc-list{font-size:var(--text-m);flex-direction:column;gap:8px;margin:0;padding:0;list-style:none;display:flex}.calc-list li{border-radius:var(--r-m);background:var(--surface-2);padding:10px 14px}.trial-chips{flex-wrap:wrap;flex:1;gap:8px;margin:0;padding:0;list-style:none;display:flex}.trial-chips li{border-radius:var(--r-pill);background:var(--surface-2);border:1px solid var(--line);font-size:var(--text-s);animation:pop .32s var(--ease) both;padding:6px 12px}.trial-chips li strong{color:var(--work)}.save-progress{font-size:var(--text-s);color:var(--ink-2);margin:-4px 0 0;font-weight:600}.exp[data-kind=assessment] .quiz,.exp[data-kind=assessment] .summary{flex:1;overflow-y:auto}.quiz{flex-direction:column;gap:22px;padding:10px 32px 28px;display:flex}.quiz-progress{align-items:center;gap:8px;display:flex}.quiz-dot{border:1.5px solid var(--line-2);width:32px;height:32px;font-size:var(--text-xs);color:var(--ink-2);border-radius:50%;place-items:center;font-weight:750;display:grid}.quiz-dot[data-state=current]{border-color:var(--accent);background:var(--accent);color:#fff;box-shadow:0 0 0 4px var(--accent-ring)}.quiz-dot[data-state=solved]{background:var(--ok-soft);border-color:var(--ok-line);color:var(--ok)}.quiz-dot[data-state=tried]{background:var(--butter);border-color:var(--hint-line)}.qcard{flex-direction:column;gap:16px;width:100%;max-width:700px;display:flex}.qcard-prompt{font-family:var(--font-display);letter-spacing:-.015em;font-size:1.45rem;font-weight:650;line-height:1.35}.qcard-prompt:focus{outline:none}.options{border:0;flex-direction:column;gap:10px;min-width:0;margin:0;padding:0;display:flex}.option{border-radius:var(--r-l);border:1.5px solid var(--line-2);background:var(--surface);cursor:pointer;transition:border-color var(--t-fast), background var(--t-fast);align-items:flex-start;gap:12px;padding:15px 18px;font-size:1.05rem;display:flex;position:relative}.option:hover{background:#fafaff;border-color:#a9a4e8}.option input{opacity:0;width:1px;height:1px;position:absolute}.option:focus-within{outline:3px solid var(--focus);outline-offset:2px}.option-mark{border:2px solid var(--line-2);background:var(--surface);width:20px;height:20px;transition:all var(--t-fast);border-radius:50%;flex-shrink:0;margin-top:4px}.option-check .option-mark{border-radius:6px}.option[data-selected]{border-color:var(--accent);background:#f6f5ff}.option[data-selected] .option-mark{border-color:var(--accent);background:var(--accent);box-shadow:inset 0 0 0 3px #fff}.option[data-state=right]{border-color:var(--ok-line);background:var(--ok-soft)}.option[data-state=wrong]{background:var(--bad-soft);border-color:#e7a8a0}.option-note{font-size:var(--text-s);margin-top:6px;display:block}.option-note svg{vertical-align:-2px}fieldset:disabled .option{cursor:default}.numeric{flex-wrap:wrap;align-items:center;gap:10px;display:flex}.numeric-label{font-weight:750;font-family:var(--font-display);font-size:1.3rem;font-style:italic}.numeric-input{border-radius:var(--r-m);border:1.5px solid var(--line-2);background:var(--surface);width:130px;height:50px;padding:0 14px;font-size:1.2rem;font-weight:700}.numeric-unit{border-radius:var(--r-m);border:1.5px solid var(--line-2);background:var(--surface);height:50px;padding:0 12px;font-size:1rem;font-weight:700}.numeric-input:focus-visible,.numeric-unit:focus-visible{outline:3px solid var(--focus);outline-offset:1px}.form-error{color:var(--bad);font-weight:700;font-size:var(--text-s)}.qcard-hint{border-radius:var(--r-m);background:var(--butter);align-items:flex-start;gap:8px;padding:12px 16px;display:flex}.qcard-hint svg{color:var(--hint);flex-shrink:0;margin-top:4px}.feedback{border-radius:var(--r-l);background:var(--butter);animation:fade-up .3s var(--ease) both;flex-direction:column;align-items:flex-start;gap:6px;padding:16px 18px;display:flex}.feedback:focus{outline:none}.feedback[data-correct=true]{background:var(--ok-soft)}.feedback-title{align-items:center;gap:6px;font-weight:750;display:flex}.feedback[data-correct=true] .feedback-title{color:var(--ok)}.feedback[data-correct=false] .feedback-title{color:#7a4300}.qcard-actions{flex-wrap:wrap;justify-content:flex-end;gap:10px;display:flex}.summary{flex-direction:column;gap:14px;padding:10px 32px 28px;display:flex}.summary-hero{border-radius:var(--r-l);background:var(--butter);align-items:flex-start;gap:16px;padding:22px 24px;display:flex}.summary-hero svg{color:#a0700c;flex-shrink:0}.summary-hero h3{margin-bottom:4px;font-size:1.55rem}.summary-hero h3:focus{outline:none}.summary-sub{margin-top:6px;font-size:1.05rem}.summary-list{flex-direction:column;gap:8px;margin:0;padding:0;list-style:none;display:flex}.summary-list li{border-radius:var(--r-m);background:var(--butter);flex-wrap:wrap;align-items:flex-start;gap:8px;padding:12px 16px;display:flex}.summary-list li[data-strong]{background:var(--ok-soft)}.summary-list li[data-strong] svg{color:var(--ok);flex-shrink:0;margin-top:5px}.summary-list li>span:first-of-type{flex:1;min-width:200px}.summary-links{flex-wrap:wrap;gap:10px;display:flex}.tutor{animation:fade-up .28s var(--ease) both;flex-direction:column;display:flex;overflow:hidden}.tutor-head{border-bottom:1px solid var(--line);align-items:center;gap:10px;padding:16px 16px 14px;display:flex}.tutor-avatar{background:var(--ink);color:#fff;border-radius:13px;flex-shrink:0;place-items:center;width:40px;height:40px;display:grid}.tutor-titles{flex:1;min-width:0}.tutor-titles h2{font-size:1.15rem}.tutor-mode{font-size:var(--text-xs);color:var(--ink-2);font-weight:700}.tutor-mode[data-live]{color:var(--ok)}.tutor-lang{border-radius:var(--r-s);border:1px solid var(--line-2);background:var(--surface);max-width:116px;height:38px;font-size:var(--text-s);padding:0 8px;font-weight:700}.tutor-log{background:var(--surface-2);flex-direction:column;flex:1;gap:12px;min-height:120px;padding:18px 16px;display:flex;overflow-y:auto}.msg{animation:fade-up .24s var(--ease) 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