:root{color-scheme:light dark;--fg:#1a1a1a;--muted:#666;--bg:#fff;--panel:#f5f5f7;--accent:#2563eb;--border:#e2e2e5}*{box-sizing:border-box}body{margin:0;font:15px/1.5 system-ui,sans-serif;color:var(--fg);background:var(--bg)}a{color:var(--accent);text-decoration:none}a:hover{text-decoration:underline}.nav{display:flex;gap:16px;align-items:center;padding:12px 20px;border-bottom:1px solid var(--border);position:sticky;top:0;background:var(--bg)}.nav .grow{flex:1}.wrap{max-width:900px;margin:0 auto;padding:20px}.card{border:1px solid var(--border);border-radius:10px;padding:14px 16px;margin:10px 0}input,button,textarea{font:inherit}input,textarea{width:100%;padding:9px 11px;border:1px solid var(--border);border-radius:8px;background:var(--panel);color:var(--fg)}button{padding:9px 14px;border:0;border-radius:8px;background:var(--accent);color:#fff;cursor:pointer}button:disabled{opacity:.5;cursor:default}.muted{color:var(--muted);font-size:13px}.tag{display:inline-block;background:var(--panel);border:1px solid var(--border);border-radius:999px;padding:1px 9px;font-size:12px;margin:2px 4px 2px 0}.center{min-height:70vh;display:grid;place-items:center}.login{width:320px}video{width:100%;border-radius:10px;background:#000}.seg{cursor:pointer;padding:2px 0}.seg:hover{background:var(--panel)}.answer{white-space:pre-wrap}.grid{display:grid;grid-template-columns:1fr;gap:2px}.module{margin:22px 0}.module-title{margin:0 0 6px;font-size:13px;text-transform:uppercase;letter-spacing:.05em;color:var(--muted);border-bottom:1px solid var(--border);padding-bottom:6px}