:root{--bg:#f6f3ec;--panel:#efeadf;--ink:#23201b;--muted:#6f685c;--line:#d9d2c3;--accent:#8a3b24;--lightningcss-light:initial;--lightningcss-dark: ;color-scheme:light dark}@media (prefers-color-scheme:dark){:root{--lightningcss-light: ;--lightningcss-dark:initial;--bg:#171512;--panel:#1f1c18;--ink:#ece6da;--muted:#a39b8c;--line:#37322a;--accent:#d98a6a}}*{box-sizing:border-box}body{background:var(--bg);color:var(--ink);margin:0;font:16px/1.6 system-ui,-apple-system,PingFang SC,Microsoft YaHei,sans-serif}.shell{grid-template-columns:220px minmax(0,1fr);min-height:100vh;display:grid}#nav{background:var(--panel);border-right:1px solid var(--line);height:100vh;padding:20px 12px;position:sticky;top:0;overflow-y:auto}#nav h1{color:var(--muted);margin:0 8px 12px;font-size:14px;font-weight:600}#nav ul{margin:0;padding:0;list-style:none}.nav-link{min-height:44px;color:inherit;border-radius:6px;justify-content:space-between;align-items:baseline;gap:8px;padding:10px 8px;text-decoration:none;display:flex}.nav-link small{color:var(--muted)}.nav-link:hover{background:color-mix(in srgb, var(--ink) 6%, transparent)}.nav-link[aria-current=page]{background:color-mix(in srgb, var(--accent) 14%, transparent);color:var(--accent)}#nav .nav-aux{border-top:1px solid var(--line);margin-top:12px;padding-top:12px}main{padding:32px clamp(16px,5vw,56px) 64px}.lesson h2{margin:0;font:600 28px/1.3 Songti SC,Noto Serif CJK SC,Source Han Serif SC,serif}.byline{color:var(--muted);margin:4px 0 20px}[role=tablist]{border-bottom:1px solid var(--line);gap:4px;margin-bottom:24px;display:flex}[role=tab]{min-height:44px;color:var(--muted);font:inherit;cursor:pointer;background:0 0;border:0;border-bottom:2px solid #0000;margin-bottom:-1px;padding:8px 16px}[role=tab][aria-selected=true]{color:var(--ink);border-bottom-color:var(--accent)}:focus-visible{outline:2px solid var(--accent);outline-offset:2px}.text{max-width:34em;font:19px/2 Songti SC,Noto Serif CJK SC,Source Han Serif SC,serif}.text p{text-indent:2em;margin:0 0 1em}.source{max-width:34em;color:var(--muted);margin-top:32px;font-size:13px}.source a{color:inherit}.scene-wrap{position:relative}.scene{aspect-ratio:3/2;background:var(--panel);touch-action:none;border-radius:8px;width:100%;height:auto;max-height:max(300px,min(640px,100svh - 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