:root{--bg:#090b0c;--panel:#121617;--panel2:#181d1e;--text:#eff1eb;--muted:#9aa39f;--line:#2b3331;--acid:#c8ff3d;--cyan:#62e5dc;--orange:#ff9157;--purple:#a78bfa;--max:1080px}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--text);font-family:Inter,ui-sans-serif,system-ui,sans-serif;line-height:1.7}.course-top{height:64px;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;padding:0 24px;position:sticky;top:0;background:rgba(9,11,12,.94);backdrop-filter:blur(12px);z-index:10}.course-top a{color:var(--text);text-decoration:none}.course-brand{font:700 12px ui-monospace,monospace;letter-spacing:.1em}.course-progress{font:11px ui-monospace,monospace;color:var(--acid)}.lesson-shell{max-width:var(--max);margin:auto;display:grid;grid-template-columns:250px minmax(0,1fr);gap:48px;padding:55px 24px 100px}.lesson-nav{position:sticky;top:95px;align-self:start}.lesson-nav .overline{font:10px 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