:root{color-scheme:light;--accent:#216be5;--ink:#243343;--muted:#64768a;--line:#dce4eb}*{box-sizing:border-box}body{margin:0;overflow:hidden;background:#f5f7fa;color:var(--ink);font-family:Inter,'PingFang SC','Microsoft YaHei',sans-serif}button,a,input{-webkit-tap-highlight-color:transparent}button{font:inherit;color:inherit;cursor:pointer;border:0;background:transparent}button:focus-visible,a:focus-visible{outline:2px solid var(--accent);outline-offset:4px}button:hover{color:var(--accent)}button:disabled{cursor:default;color:#8b99a6;opacity:.55}#stage{position:absolute;left:0;right:320px;top:128px;bottom:142px;background:#edf2f5;overflow:hidden}#stage canvas{display:block;width:100%;height:100%;touch-action:none}.vignette{display:none}header{position:absolute;left:0;right:0;top:0;height:78px;padding:0 32px;display:flex;align-items:center;justify-content:space-between;background:#fff;border-bottom:1px solid var(--line);z-index:3}.brand{color:#233449;text-decoration:none;font-size:22px;font-weight:650;letter-spacing:.5px;display:flex;align-items:center;gap:16px}.brand:before{content:'◎';display:grid;place-items:center;background:#e8f0ff;color:#216be5;border-radius:12px;width:40px;height:40px;font-size:30px;font-weight:400}.brand span{font-family:Arial,sans-serif;font-size:10px;letter-spacing:1.6px;color:#7f91a1;border-left:1px solid var(--line);padding-left:16px;font-weight:400}.top-right{display:flex;align-items:center;gap:22px;font-size:12px;color:#5d7082}.subject{color:#748596;margin-right:10px}.top-right button{padding:8px 0}.story{position:absolute;right:0;left:auto;top:78px;bottom:0;width:320px;padding:38px 27px;background:#fff;border-left:1px solid var(--line);z-index:4}.chapter{display:flex;align-items:center;gap:12px;font-size:12px;color:#596f83;letter-spacing:1px}.chapter>span:first-child{font:600 13px Arial,sans-serif;color:var(--accent);background:#eaf1ff;border-radius:6px;padding:7px}.chapter button{font-size:19px;margin-left:auto}.story h1{font-size:28px;line-height:1.5;letter-spacing:-.5px;font-weight:650;margin:22px 0 15px;white-space:pre-line}.story>p{font-size:13px;color:#6b7c8b;line-height:1.9;margin:0}.action{padding:16px;background:#f2f6fb;border-radius:10px;margin-top:25px}.small-label{font-size:11px;font-weight:600;color:#607b94;letter-spacing:.5px}.action p{font-size:14px;line-height:1.8;margin:7px 0 0;color:#304d68}#discovery{font-size:12px;line-height:1.9;color:#19726d;min-height:48px;margin-top:17px}.continue{margin-top:20px}.continue>button:first-child{display:block;background:var(--accent);color:#fff;padding:13px 16px;border-radius:8px;font-size:13px;text-align:center;width:100%;box-shadow:0 4px 10px #216be515}.continue>button:first-child:hover{background:#155bcf}.back{font-size:12px;color:#6e8090;margin-top:18px;padding:0}.back:disabled{visibility:hidden}#chapterMenu{position:absolute;top:75px;left:20px;right:20px;background:white;border:1px solid var(--line);border-radius:10px;padding:8px;z-index:10;box-shadow:0 10px 35px #213e5020}#chapterMenu button{display:block;text-align:left;width:100%;padding:12px;font-size:13px;border-radius:5px}#chapterMenu button.active{color:var(--accent);background:#edf4ff}.scene-caption{position:absolute;left:29px;top:147px;display:flex;align-items:center;gap:8px;font-size:11px;letter-spacing:.3px;color:#5c7587;z-index:2;pointer-events:none}.dot{width:6px;height:6px;background:#3b9c98;border-radius:50%}.viewbar{position:absolute;top:78px;left:0;right:320px;height:50px;display:flex;align-items:center;gap:8px;padding:0 24px;background:#fff;border-bottom:1px solid var(--line);white-space:nowrap}.viewbar button{height:100%;padding:0 14px;font-size:12px;color:#6b7f91;position:relative}.viewbar button.selected{color:var(--accent);font-weight:600}.viewbar button.selected:after{content:'';height:3px;background:var(--accent);position:absolute;bottom:0;left:13px;right:13px;border-radius:3px}.viewbar span{width:1px;height:16px;background:var(--line);margin:0 8px}.viewbar #rays.active{color:#b76621}.viewbar #illumination{margin-left:auto;font-size:11px}.console{position:absolute;bottom:0;left:0;right:320px;height:142px;display:flex;align-items:center;gap:26px;padding:22px 28px 34px;border-top:1px solid var(--line);background:#fff}.control{flex:1;min-width:145px}.control label{display:flex;justify-content:space-between;font-size:12px;gap:10px;margin-bottom:18px}.control output{color:#355a7c;font-variant-numeric:tabular-nums;font-size:13px}.control i{display:inline-block;width:7px;height:7px;border-radius:50%;margin-right:7px}.object-dot{background:#e89242}.screen-dot{background:#3d8bcc}input[type=range]{width:100%;height:4px;accent-color:#377de0;cursor:ew-resize;display:block;margin:0}#object{accent-color:#d5883b}.ticks{display:flex;justify-content:space-between;color:#8191a0;font-size:10px;margin-top:13px}.observation{width:166px;border-left:1px solid var(--line);padding-left:22px;min-height:72px}.observation strong{font-weight:550;font-size:14px;display:block;margin:8px 0;color:#375267}.observation>span:last-child{font-size:10px;color:#7a8997;line-height:1.6;display:block}#reset{font-size:11px;color:#768796;padding:8px;border:1px solid var(--line);border-radius:6px}.model-note{position:absolute;bottom:13px;left:28px;font-size:10px;color:#8392a0;letter-spacing:.3px}#labels{position:absolute;inset:0;pointer-events:none}.label{position:absolute;font-size:11px;color:#486276;padding:5px 9px;background:#ffffffeb;border:1px solid #d5e0e8;border-radius:5px;white-space:nowrap;transform:translate(-50%,-50%);box-shadow:0 2px 8px #3c5e7710}dialog{max-width:550px;padding:30px;background:#fff;color:#596d7d;border:1px solid var(--line);border-radius:12px}dialog::backdrop{background:#18334660;backdrop-filter:blur(5px)}dialog h2{font-size:21px;font-weight:550;color:#244f71}dialog p{font-size:14px;line-height:1.9}#closeHelp{float:right;color:var(--accent)}#webglError{position:absolute;inset:35% 20%;padding:30px;color:#854619;background:#fff4e2;z-index:30}@media(max-height:800px){.story{padding-top:27px}.story h1{font-size:26px;margin:18px 0 12px}.action{margin-top:18px;padding:13px}.continue{margin-top:14px}#discovery{margin-top:12px;min-height:42px}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto}}

/* Controls stay beside their objects; the scene remains freely navigable. */
#stage canvas{cursor:grab}.scene-tools{position:absolute;right:338px;top:141px;display:flex;gap:7px;z-index:2}.scene-tools button{background:#fffffff0;border:1px solid #d2dfe9;border-radius:7px;padding:7px 11px;font-size:11px;color:#42637d}.label:has(button){padding:0;pointer-events:auto;display:flex;align-items:center;border-radius:8px;box-shadow:0 3px 12px #36566b16}.label[hidden]{display:none}.object-handle{padding:9px 11px;cursor:ew-resize;touch-action:none;font-size:12px;font-weight:600}.object-handle span{font-size:11px;font-weight:400;color:#698090;margin-left:5px;font-variant-numeric:tabular-nums}#label-candle{border-bottom:2px solid #ca873f}#label-screen{border-bottom:2px solid #337fd2}#inspectScreen{border-left:1px solid #d5e0e8;padding:9px;color:#216be5;font-size:11px}#label-axis{background:none;border:0;box-shadow:none;color:#657e8e;font-size:10px}#label-o,#label-f1,#label-f2,#label-ff1,#label-ff2{padding:2px 4px;font:11px Arial;background:#ffffffe0;border:0;box-shadow:none}#rayLegend{position:absolute;left:25px;bottom:161px;padding:12px 15px;background:#fffffff0;border:1px solid #dbe5ec;border-radius:9px;pointer-events:none;color:#536e82;box-shadow:0 3px 15px #38587009}#rayLegend strong{display:block;font-size:11px;font-weight:500;color:#61788b;margin-bottom:7px}#rayLegend span{display:block;font-size:12px;line-height:1.85}#rayLegend small{display:block;font-size:10px;color:#788b99;margin-top:5px}#rayLegend [hidden]{display:none}#rayLegend i{display:inline-block;width:21px;height:2px;vertical-align:middle;margin-right:8px}.ray-orange{background:#c2691d}.ray-blue{background:#236fca}

/* Keep the key above the apparatus handles, not over the drag target. */
#rayLegend{top:184px;bottom:auto;max-width:340px}
#rayLegend strong{font-size:13px;color:#344d61}
#rayLegend span{font-size:13px;color:#344d61}
#rayLegend small{font-size:12px;color:#526a7d}
.scene-caption{font-size:12px;color:#40586c}
#label-o,#label-f1,#label-f2,#label-ff1,#label-ff2{font-size:13px;color:#344d61}
#label-axis{font-size:12px;color:#425d70;background:#f4f7fae8;padding:3px 6px;border-radius:4px}