:root{--bg: #f6f6f4;--surface: #ffffff;--ink: #1b1b1a;--muted: #6b6b66;--line: #dcdcd6;--accent: #1f5fa8;--ok: #17794a;--bad: #b03030;--warn: #9a6b0f;--radius: 8px;color-scheme:light dark}@media(prefers-color-scheme:dark){:root{--bg: #16171a;--surface: #1e2024;--ink: #e8e8e6;--muted: #9b9b95;--line: #33353b;--accent: #78aee8;--ok: #59c08d;--bad: #e58a8a;--warn: #d9b166}}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font:15px/1.5 ui-sans-serif,system-ui,-apple-system,Segoe UI,sans-serif}.app-bar{display:flex;align-items:center;gap:20px;padding:10px 20px;border-bottom:1px solid var(--line);background:var(--surface);position:sticky;top:0;z-index:5}.brand{font-weight:650;text-decoration:none;color:var(--ink);letter-spacing:.01em}.app-bar nav{display:flex;gap:16px}.app-bar nav a{color:var(--muted);text-decoration:none;font-size:14px}.app-bar nav a.active,.app-bar nav a:hover{color:var(--accent)}.app{padding:20px;max-width:1400px;margin:0 auto}h1{font-size:20px;margin:0 0 4px}h2{font-size:16px;margin:0 0 8px}h3{font-size:14px;margin:0 0 6px}p.sub{color:var(--muted);margin:0 0 18px;font-size:14px}.card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:16px;margin-bottom:16px}label{display:block;font-size:13px;color:var(--muted);margin-bottom:4px}input[type=text],input[type=number],textarea,select{width:100%;padding:8px 10px;font:inherit;color:var(--ink);background:var(--bg);border:1px solid var(--line);border-radius:6px}textarea{resize:vertical;min-height:90px;font-family:ui-monospace,Cascadia Code,monospace;font-size:14px}.field{margin-bottom:12px}.row{display:flex;gap:12px;flex-wrap:wrap}.row>*{flex:1 1 180px}button{font:inherit;padding:7px 13px;border-radius:6px;border:1px solid var(--line);background:var(--surface);color:var(--ink);cursor:pointer}button:hover{border-color:var(--accent);color:var(--accent)}button.primary{background:var(--accent);border-color:var(--accent);color:#fff}button.primary:hover{filter:brightness(1.08);color:#fff}button.danger:hover{border-color:var(--bad);color:var(--bad)}button:disabled{opacity:.5;cursor:not-allowed}.actions{display:flex;gap:8px;flex-wrap:wrap;align-items:center}.muted{color:var(--muted);font-size:13px}.warn{color:var(--warn)}.error{color:var(--bad)}.list{display:grid;gap:10px}.list-item{display:flex;align-items:center;gap:14px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:12px 14px}.list-item .grow{flex:1;min-width:0}.list-item a{color:var(--ink);text-decoration:none;font-weight:600}.list-item a:hover{color:var(--accent)}.progress{height:6px;background:var(--line);border-radius:99px;overflow:hidden;width:160px}.progress>span{display:block;height:100%;background:var(--ok)}.workspace{display:grid;grid-template-columns:230px minmax(0,1fr);gap:18px;align-items:start}@media(max-width:860px){.workspace{grid-template-columns:1fr}}.problem-list{display:grid;gap:4px;position:sticky;top:70px;max-height:calc(100vh - 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