:root{color-scheme:light dark;--bg:#111418;--surface:#1b2026;--line:#343c46;--text:#edf0f4;--muted:#a8b2c0;--accent:#8cb4e7;--button:#b5d0f2;--button-text:#10233e;--selected:#273b53}
html[data-theme=light]{color-scheme:light;--bg:#f4f6f9;--surface:#fff;--line:#d2dae4;--text:#172436;--muted:#52647a;--accent:#225b9d;--button:#225b9d;--button-text:#fff;--selected:#eaf2ff}
@media(prefers-color-scheme:light){html:not([data-theme=dark]){color-scheme:light;--bg:#f4f6f9;--surface:#fff;--line:#d2dae4;--text:#172436;--muted:#52647a;--accent:#225b9d;--button:#225b9d;--button-text:#fff;--selected:#eaf2ff}}
*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--text);font:15px/1.65 system-ui,-apple-system,sans-serif}a{color:var(--accent);text-underline-offset:4px}a:focus-visible,button:focus-visible,video:focus-visible,summary:focus-visible{outline:2px solid var(--accent);outline-offset:4px}.skip{position:absolute;left:12px;top:-60px;background:var(--surface);padding:10px;z-index:2}.skip:focus{top:10px}header{border-bottom:1px solid var(--line)}.bar{max-width:1280px;margin:auto;display:flex;align-items:center;gap:20px;padding:16px 24px}.brand{display:flex;align-items:center;gap:9px;color:var(--text);text-decoration:none}.brand img{width:32px;height:32px}.brand span{font-size:12px;color:var(--muted)}nav{margin-left:auto;display:flex;align-items:center;gap:18px}nav a,nav button{font-size:13px}nav a[aria-current=page]{color:var(--text);text-decoration:none}button{font:inherit;cursor:pointer}nav button{background:var(--surface);color:var(--text);border:1px solid var(--line);padding:5px 9px;border-radius:5px}main{max-width:1280px;margin:auto;padding:28px 24px 36px}.intro{display:flex;justify-content:space-between;gap:24px;margin-bottom:24px}.eyebrow{font-size:12px!important;letter-spacing:.05em;color:var(--accent)!important;margin:0 0 8px!important}h1{font-size:30px;line-height:1.3;letter-spacing:-.03em;margin:0 0 12px}h2{font-size:20px;margin:0 0 10px}.intro p,.resources>p{color:var(--muted);margin:0;max-width:720px;font-size:14px}.mobile-break{display:none}.spec{display:flex;flex-direction:column;align-items:flex-end;justify-content:center;gap:4px;font:12px/1.6 ui-monospace,monospace;color:var(--muted);white-space:nowrap}.spec span:first-child{color:var(--text);font-size:21px;font-variant-numeric:tabular-nums}.lesson{display:grid;grid-template-columns:minmax(0,1fr) 280px;gap:20px;align-items:start}.player-panel{min-width:0}video{display:block;width:100%;aspect-ratio:16/9;background:#050608;border:1px solid var(--line);border-radius:7px}video::cue{background:rgba(0,0,0,.8);color:#fff}.transport{display:flex;align-items:center;gap:12px;min-height:56px;border-bottom:1px solid var(--line)}#play-toggle{background:var(--button);color:var(--button-text);border:0;border-radius:4px;padding:7px 13px;font-size:13px;white-space:nowrap}#playback-state{font-size:12px;color:var(--muted)}#playback-clock{margin-left:auto;font:12px/1.5 ui-monospace,monospace;font-variant-numeric:tabular-nums;white-space:nowrap}.version-note{color:var(--muted);font-size:12px;line-height:1.6;margin:10px 0 0}.chapters{border:1px solid var(--line);border-radius:7px;background:var(--surface);overflow:hidden}.chapter-head{padding:13px 16px;border-bottom:1px solid var(--line);display:flex;justify-content:space-between;align-items:center}.chapter-head h2{font-size:15px;margin:0}.chapter-head>span{font:11px/1.6 ui-monospace,monospace;color:var(--muted)}.chapters ol{list-style:none;padding:5px 0;margin:0}.chapters button{display:flex;align-items:center;gap:12px;width:100%;text-align:left;background:transparent;border:0;border-left:2px solid transparent;color:var(--text);padding:10px 14px;font-size:12px;line-height:1.5}.chapters button:hover{background:var(--selected)}.chapters button[aria-current=true]{border-left-color:var(--accent);background:var(--selected)}.chapters time{font:11px/1.5 ui-monospace,monospace;font-variant-numeric:tabular-nums;color:var(--muted);min-width:35px}.chapters>p{font-size:11px;color:var(--muted);padding:12px 16px;margin:0;border-top:1px solid var(--line)}.resources{padding:26px 0;margin-top:25px;border-top:1px solid var(--line)}.resource-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px;margin:18px 0}.resource{display:flex;flex-direction:column;gap:7px;padding:17px;background:var(--surface);border:1px solid var(--line);border-radius:6px;text-decoration:none}.resource strong{font-size:13px;font-weight:600}.resource span{font-size:11px;color:var(--muted)}.resource:hover{border-color:var(--accent)}.resource.primary{border-color:var(--accent)}.extra{display:flex;flex-wrap:wrap;gap:10px 24px;font-size:12px}.scope{padding:15px 0;border-top:1px solid var(--line);font-size:13px}.scope summary{cursor:pointer}.scope p{color:var(--muted);max-width:920px}footer{display:flex;gap:20px;flex-wrap:wrap;padding-top:18px;margin-top:14px;border-top:1px solid var(--line);font-size:12px;color:var(--muted)}footer span{margin-right:auto}
@media(max-width:1000px){.brand span{display:none}.lesson{grid-template-columns:minmax(0,1fr) 245px}.chapters button{gap:8px;padding:10px}.resource-grid{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media(max-width:760px){.bar{padding:12px 16px;gap:12px;flex-wrap:wrap}.brand img{width:26px;height:26px}nav{gap:12px}nav a,nav button{font-size:12px}main{padding:23px 16px 30px}.intro{display:block;margin-bottom:18px}h1{font-size:25px}.spec{flex-direction:row;justify-content:flex-start;align-items:baseline;gap:10px;margin-top:16px;white-space:normal}.spec span:first-child{font-size:15px}.lesson{grid-template-columns:1fr;gap:18px}.chapters ol{display:grid;grid-template-columns:repeat(2,minmax(0,1fr))}.chapters button{height:100%;min-height:46px}.chapters>p{font-size:12px}.transport{flex-wrap:wrap;gap:8px;padding:8px 0}.resources{margin-top:22px}.resource{padding:14px}#playback-state{font-size:11px}}
@media(max-width:430px){nav{width:100%;margin-left:0;justify-content:space-between}.mobile-break{display:block}.chapters ol{grid-template-columns:1fr}.chapters button{font-size:13px;padding:9px 15px;min-height:40px}.spec{font-size:11px;gap:10px}.resource-grid{grid-template-columns:1fr}#playback-clock{font-size:11px}.transport{gap:8px}#play-toggle{padding:7px 10px;font-size:12px}}