:root{color-scheme:light;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;color:var(--text);background:var(--page);font-synthesis:none;text-rendering:optimizeLegibility;--page: #eef5f4;--surface: #ffffff;--surface-soft: #f7fbfa;--surface-strong: rgba(255, 255, 255, .94);--text: #111827;--muted: #4b5563;--border: #d5e2e0;--border-strong: #b7c8c6;--accent: #256f73;--accent-strong: #17494c;--accent-soft: #e5f0ee;--warning: #d97706;--warning-soft: #fff8ed;--success: #12805c;--success-soft: #edf9f4;--danger: #b42318;--chip: #e2eeee;--edge: #7b8d8b;--node-dark: #1f2937;--node-dark-border: #111827;--node-red: #d1403f;--node-red-border: #8f1d1d}:root[data-theme=dark]{color-scheme:dark;--page: #111827;--surface: #18212f;--surface-soft: #202b3a;--surface-strong: rgba(24, 33, 47, .94);--text: #f4f7f6;--muted: #b8c4c2;--border: #334155;--border-strong: #5b6b7d;--accent: #5ec5be;--accent-strong: #8be0da;--accent-soft: #203b42;--warning: #f5b35e;--warning-soft: #382818;--success: #6ee7b7;--success-soft: #17362f;--danger: #ff8b8b;--chip: #243947;--edge: #8796a8;--node-dark: #020617;--node-dark-border: #64748b;--node-red: #c2414b;--node-red-border: #fecaca}*{box-sizing:border-box}body{margin:0;background:var(--page)}button,input,textarea,select{font:inherit}main{max-width:1180px;margin:0 auto;padding:28px 18px 56px}.topbar{display:flex;align-items:center;justify-content:space-between;gap:20px;padding:22px 0 28px}h1,h2,p{margin:0}h1{font-size:clamp(2rem,4vw,3.2rem);font-weight:800}.topbar p{margin-top:8px;color:var(--muted)}.actions,.submit-band{display:flex;gap:10px;align-items:center}button{border:1px solid var(--border-strong);border-radius:8px;background:var(--surface);color:var(--text);padding:10px 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0}.solution.correct{border-left-color:var(--success);background:var(--success-soft)}.solution p{margin-top:8px}.viz{margin-top:14px;border:1px solid var(--border);border-radius:8px;background:var(--surface-soft);overflow:auto}.viz-title{padding:10px 12px;font-weight:800;color:var(--accent);border-bottom:1px solid var(--border)}svg{display:block;min-width:680px;width:100%;height:auto}.edge{stroke:var(--edge);stroke-width:2.2}.black-node{fill:var(--node-dark);stroke:var(--node-dark-border);stroke-width:2}.red-node{fill:var(--node-red);stroke:var(--node-red-border);stroke-width:2}.heap-node{fill:var(--accent);stroke:var(--accent-strong);stroke-width:2}.node-text{fill:#fff;font-size:16px;font-weight:800}.array-steps{display:grid;gap:8px;margin-top:12px}.array-step{display:grid;grid-template-columns:190px 1fr;gap:10px;align-items:center}.array-step span{color:var(--muted)}.chips{display:flex;flex-wrap:wrap;gap:6px}.chips b,.snapshots span{min-width:34px;padding:6px 8px;border-radius:6px;background:var(--chip);text-align:center}.snapshots{display:flex;flex-wrap:wrap;gap:8px;padding:12px}.muted{color:var(--muted)}.submit-band{justify-content:center;padding:24px 0 0}@media(max-width:720px){main{padding-inline:12px}.topbar,.status,.task-head{flex-direction:column;align-items:stretch}.mode-grid{grid-template-columns:1fr}.actions{display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr))}.rb-row,.array-step{grid-template-columns:1fr}}