:root{--paper:#fbf7f0;--ink:#2d3440;--muted:#64717e;--border:#e1e5e9;--accent:#247caa}*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font:15px/1.6 "Microsoft YaHei","PingFang SC",sans-serif}button,select,input{font:inherit}button,select{border:1px solid #d8dfe6;border-radius:8px;background:#fff;color:var(--ink);padding:7px 13px}button{cursor:pointer}button:hover{background:#edf4f8}button:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible{outline:3px solid #4c9fc6;outline-offset:3px}button:disabled{opacity:.5}h1,h2,h3,p{margin:0}h1{font-size:27px;letter-spacing:1px}h2{font-size:25px;margin:0 0 9px}h3{font-size:15px;margin-bottom:6px}.engine-app{max-width:1540px;margin:auto;padding:16px 24px}header{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px}.eyebrow{font-size:12px;letter-spacing:1px;color:var(--muted)}.intro{color:var(--muted);font-size:14px}.strokes{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;margin-bottom:12px}.strokes button{text-align:left;font-size:18px;font-weight:700;border-bottom:3px solid #d8dfe6;padding:9px 15px}.strokes small{font-size:12px;opacity:.7;margin-right:6px}.strokes span{display:block;font-size:12px;font-weight:400;margin-left:28px}.strokes button[aria-pressed=true]{border-color:var(--accent);background:#edf5fa;color:var(--accent)}.lesson-grid{display:grid;grid-template-columns:minmax(0,1fr) 315px;gap:16px}.model-panel{border:1px solid var(--border);border-radius:12px;background:#fff;overflow:hidden;display:flex;flex-direction:column}.view-tools{display:flex;align-items:center;justify-content:space-between;padding:8px 14px;font-size:12px;border-bottom:1px solid #edf0f2}.view-tools>div{display:flex;align-items:center;gap:8px}.view-tools button{font-size:12px;padding:4px 9px}#viewport{position:relative;height:clamp(320px,calc(100vh - 470px),660px);min-height:320px;touch-action:none;background-color:#fcfdfe;background-image:linear-gradient(#edf1f588 1px,transparent 1px),linear-gradient(90deg,#edf1f588 1px,transparent 1px);background-size:28px 28px}canvas{display:block;width:100%;height:100%;position:absolute;inset:0}#loading{position:absolute;inset:0;display:grid;place-content:center;background:#fff;z-index:6;padding:30px;text-align:center}#leaders,#annotations{position:absolute;inset:0;width:100%;height:100%;pointer-events:none;z-index:2}#leaders path{stroke:#8a9aaa;stroke-width:1;fill:none}#leaders circle{fill:#5b7084}.part-label{position:absolute;font-size:12px;background:#ffffffed;border:1px solid #e1e7ec;border-radius:5px;padding:2px 7px;white-space:nowrap}#event-badge{position:absolute;bottom:12px;left:50%;transform:translateX(-50%);padding:4px 16px;background:#edf5faeb;color:#247caa;border:1px solid #cddfe9;border-radius:20px;font-size:13px;white-space:nowrap;z-index:3}.canvas-help{text-align:center;color:var(--muted);font-size:11px;padding-top:5px}.legend{display:flex;gap:18px;justify-content:center;padding:5px 8px 8px;font-size:11px}.legend i{display:inline-block;width:8px;height:8px;border-radius:50%;margin-right:5px}.blue{background:var(--gas-mixture,#55c6f2)}.orange{background:var(--gas-hot,#ffb34d)}.gray{background:var(--gas-exhaust,#b8c4ce)}aside{background:white;border:1px solid var(--border);border-radius:12px;padding:17px 19px}#phase-description{font-size:14px;min-height:67px}.state-list{margin:12px 0}.state-list>div{display:flex;justify-content:space-between;padding:5px 0;border-bottom:1px solid #edf0f2}.state-list dt{color:var(--muted)}.state-list dd{margin:0;font-weight:bold}.open{color:#247caa}.energy{border-left:3px solid var(--accent);padding:6px 12px;background:#f6f8fa}.energy p,.observe p,details p{font-size:13px}.observe{margin:12px 0}summary{font-size:12px;cursor:pointer;color:#51687d}details p{padding-top:8px}.playback{background:white;border:1px solid var(--border);border-radius:12px;padding:10px 16px;margin-top:12px}.play-row{display:flex;align-items:center;gap:12px;font-size:13px}.primary{background:#247caa;color:#fff;border-color:#247caa;min-width:95px}.primary:hover{background:#186991}#angle-output{margin-left:auto;font-variant-numeric:tabular-nums;color:#526372}.play-row select{padding:4px 8px}.play-row label{display:flex;align-items:center;gap:5px}#timeline{width:100%;margin:10px 0 0;accent-color:var(--accent);cursor:pointer}.ticks{display:flex;justify-content:space-between;font-size:11px;color:#687787}footer{padding-top:10px}.facts{display:flex;justify-content:center;gap:30px;font-size:13px}.facts b{margin-left:6px}footer>p{text-align:center;color:#7d858d;font-size:10px;margin-top:5px}@media(min-width:1000px) and (max-height:800px){.engine-app{padding:10px 20px}header{margin-bottom:8px}h1{font-size:23px}.strokes button{padding:6px 12px}.strokes{margin-bottom:9px}aside{padding:12px 16px}h2{font-size:22px}.state-list{margin:8px 0}.observe{margin:8px 0}.playback{margin-top:8px;padding:8px 14px}#viewport{height:calc(100vh - 430px);min-height:305px}}@media(max-width:850px){.engine-app{padding:12px}.intro{display:none}.lesson-grid{grid-template-columns:1fr}.strokes{gap:5px}.strokes button{font-size:15px;padding:7px}.strokes span{font-size:10px;margin-left:0}.strokes small{display:none}#viewport{height:420px}.play-row{flex-wrap:wrap;gap:8px}#angle-output{margin-left:0}.facts{gap:10px;flex-wrap:wrap}.view-tools{padding:7px;font-size:11px}.view-tools>div{gap:4px}.view-tools button{padding:4px 6px}.legend{gap:9px;font-size:10px}aside{padding:16px}#phase-description{min-height:0}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto}}

@media(min-width:1000px) and (max-height:800px){aside{line-height:1.5}#phase-description{min-height:56px;font-size:13px}.state-list>div{padding:3px 0}.energy{padding:5px 10px}.energy p,.observe p{font-size:12px}h3{font-size:14px;margin-bottom:4px}.observe{margin:8px 0}.view-tools{padding:6px 12px}}

.view-tools{flex-wrap:wrap;gap:4px}.view-tools>div{flex-wrap:wrap}@media(max-width:450px){.view-tools>span{display:none}.view-tools>div{width:100%;justify-content:space-between}.view-tools button{padding:4px 5px}.canvas-help{font-size:10px}}

body:has(.lesson-home-close) .intro{padding-right:75px}

/* Cutaway engine stage: silver machinery against a dark studio background. */
.model-panel{background:#242d38;border-color:#34414f;box-shadow:0 12px 30px #182b4212}
.view-tools{border-color:#ffffff13;color:#c8d4df;background:#293441;padding:10px 14px}
.view-tools button{background:#354352;color:#e2ebf4;border-color:#4b5b6d;border-radius:6px}
.view-tools button:hover{background:#496074}.view-tools input{accent-color:#6dbbe7}
#viewport{height:calc(100vh - 370px);min-height:390px;background:radial-gradient(ellipse at 50% 40%,#3b4856 0%,#2e3743 46%,#232b35 100%)}
#leaders path{stroke:#a8bdcd;opacity:.47}#leaders circle{fill:#dae9f4}
.part-label{background:#263240d9;border-color:#506376;color:#d6e6f2;font-size:11px;padding:3px 8px}
#event-badge{top:16px;right:16px;bottom:auto;left:auto;transform:none;max-width:calc(100% - 32px);background:#142737ed;color:#bce6ff;border-color:#40607a;border-radius:10px;padding:8px 16px;font-size:clamp(18px,1.6vw,22px);font-weight:600;line-height:1.5;white-space:normal;letter-spacing:.5px;pointer-events:none}
.canvas-help{color:#9babbd;padding-top:7px}.legend{color:#c0d0df;padding-bottom:10px}
aside{display:flex;flex-direction:column}.playback{margin-top:auto;padding:11px 0 0;border:0;border-top:1px solid #e2e8ee;border-radius:0;background:transparent}
.play-row{flex-wrap:wrap;gap:7px;font-size:12px}.play-row button{padding:6px 10px}.play-row select{font-size:12px;padding:3px 6px}.play-row label{font-size:11px}#angle-output{font-size:11px;margin-left:0;width:100%}
.ticks{font-size:9px}.ticks span:nth-child(3){font-size:0}.ticks span:nth-child(3)::after{content:'360°';font-size:9px}
#timeline{margin-top:6px}.observe{margin:10px 0}details{margin-bottom:12px}
.strokes button[aria-pressed=true]{background:#fff;border-bottom-width:3px;box-shadow:0 3px 10px #243c5410}
@media(min-width:1000px) and (max-height:800px){#viewport{height:calc(100vh - 330px);min-height:385px}.view-tools{padding:7px 12px}aside{padding:12px 16px}#phase-description{min-height:0}.state-list{margin:9px 0}.observe{margin:9px 0}.playback{padding-top:8px}.play-row{gap:5px}.play-row button{padding:5px 8px}details{margin-bottom:9px}}
@media(max-width:850px){#viewport{height:520px;min-height:0}aside{gap:3px}.playback{margin-top:12px;padding-top:12px}.play-row{gap:10px}.view-tools{padding:8px}.part-label{font-size:10px;padding:3px 5px}}