@import "https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=JetBrains+Mono:wght@400;600&display=swap";*{box-sizing:border-box;margin:0;padding:0}:root{--bg:#0a0a0f;--surface:#111118;--surface2:#1a1a24;--border:#2a2a3a;--text:#e2e8f0;--muted:#64748b;--radius:12px}body{background:var(--bg);color:var(--text);min-height:100vh;font-family:Inter,sans-serif}nav{-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px);border-bottom:1px solid var(--border);z-index:100;background:#0a0a0ff2;justify-content:space-between;align-items:center;height:56px;padding:0 2rem;display:flex;position:sticky;top:0}nav .brand{color:#fff;align-items:center;gap:8px;font-size:1.1rem;font-weight:700;text-decoration:none;display:flex}nav .brand span{color:#6366f1}nav .back-btn{background:var(--surface2);border:1px solid var(--border);color:var(--text);cursor:pointer;border-radius:8px;align-items:center;gap:6px;padding:6px 14px;font-size:.85rem;text-decoration:none;transition:background .2s;display:flex}nav .back-btn:hover{background:var(--border)}.home{max-width:1200px;margin:0 auto;padding:3rem 2rem}.hero{text-align:center;margin-bottom:3rem}.hero h1{background:linear-gradient(135deg,#fff 0%,#6366f1 50%,#a78bfa 100%);-webkit-text-fill-color:transparent;-webkit-background-clip:text;margin-bottom:1rem;font-size:clamp(2rem,5vw,3.5rem);font-weight:700;line-height:1.2}.hero p{color:var(--muted);max-width:600px;margin:0 auto;font-size:1.1rem}.stats{flex-wrap:wrap;justify-content:center;gap:2rem;margin-top:1.5rem;display:flex}.stat{text-align:center}.stat .num{color:#6366f1;font-size:2rem;font-weight:700}.stat .label{color:var(--muted);text-transform:uppercase;letter-spacing:1px;font-size:.8rem}.category-grid{grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:1rem;display:grid}.category-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);cursor:pointer;padding:1.5rem;text-decoration:none;transition:transform .2s,box-shadow .2s;display:block;position:relative;overflow:hidden}.category-card:hover{transform:translateY(-3px);box-shadow:0 8px 30px #0006}.category-card:before{content:"";background:var(--card-color);height:3px;position:absolute;top:0;left:0;right:0}.card-header{justify-content:space-between;align-items:flex-start;margin-bottom:.75rem;display:flex}.card-icon{color:var(--card-color);font-family:JetBrains Mono,monospace;font-size:1.2rem;font-weight:600;line-height:1}.card-count{background:var(--surface2);border:1px solid var(--border);color:var(--muted);border-radius:20px;padding:2px 8px;font-size:.75rem}.card-name{color:#fff;margin-bottom:.25rem;font-size:1rem;font-weight:600}.card-tagline{color:var(--card-color);margin-bottom:.5rem;font-size:.8rem;font-weight:500}.card-concept{color:var(--muted);font-size:.8rem;line-height:1.5}.category-page{max-width:1100px;margin:0 auto;padding:2rem}.cat-header{border-radius:var(--radius);border:1px solid var(--border);background:var(--surface);margin-bottom:1.5rem;padding:2rem}.cat-header h1{color:#fff;margin-bottom:.5rem;font-size:1.8rem;font-weight:700}.cat-concept{color:var(--muted);max-width:700px;margin-bottom:1rem;line-height:1.7}.visual-explainer{border:1px solid var(--border);border-radius:var(--radius);background:#0000004d;margin-bottom:2rem;padding:1.5rem}.visual-explainer h3{color:var(--muted);text-transform:uppercase;letter-spacing:2px;margin-bottom:1rem;font-size:.7rem}.problems-grid{grid-template-columns:repeat(auto-fill,minmax(320px,1fr));gap:.75rem;display:grid}.problem-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);cursor:pointer;justify-content:space-between;align-items:center;gap:1rem;padding:1.25rem 1.5rem;text-decoration:none;transition:border-color .2s,background .2s;display:flex}.problem-card:hover{background:var(--surface2);border-color:var(--muted)}.problem-info{flex:1;min-width:0}.problem-num{color:var(--muted);font-family:JetBrains Mono,monospace;font-size:.75rem}.problem-title{color:#fff;margin:2px 0;font-size:.95rem;font-weight:600}.badge{white-space:nowrap;border-radius:20px;padding:2px 8px;font-size:.7rem;font-weight:600}.badge.Easy{color:#22c55e;background:#22c55e26;border:1px solid #22c55e4d}.badge.Medium{color:#eab308;background:#eab30826;border:1px solid #eab3084d}.badge.Hard{color:#ef4444;background:#ef444426;border:1px solid #ef44444d}.problem-page{max-width:1000px;margin:0 auto;padding:2rem}.problem-page-header{margin-bottom:2rem}.problem-page-header h1{color:#fff;margin-bottom:.75rem;font-size:1.8rem;font-weight:700}.problem-meta{flex-wrap:wrap;align-items:center;gap:.75rem;display:flex}.lc-link{color:var(--muted);border:1px solid var(--border);border-radius:6px;padding:3px 10px;font-size:.8rem;text-decoration:none;transition:color .2s}.lc-link:hover{color:#fff}.complexity-pill{color:var(--muted);border:1px solid var(--border);border-radius:6px;padding:3px 10px;font-family:JetBrains Mono,monospace;font-size:.75rem}.section-label{text-transform:uppercase;letter-spacing:2px;color:var(--muted);margin-bottom:.75rem;font-size:.7rem;font-weight:600}.insight-box{border-radius:var(--radius);color:#c4b5fd;background:linear-gradient(135deg,#6366f11a,#a78bfa0d);border:1px solid #6366f14d;margin-bottom:1.5rem;padding:1.25rem 1.5rem;font-size:.9rem;line-height:1.6}.description-box{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);margin-bottom:1.5rem;padding:1.25rem 1.5rem;font-size:.9rem;line-height:1.6}.trace-table{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);margin-bottom:1.5rem;overflow:hidden}.trace-header{background:var(--surface2);border-bottom:1px solid var(--border);text-transform:uppercase;letter-spacing:1px;color:var(--muted);grid-template-columns:1fr 2fr 1fr;gap:1rem;padding:.75rem 1.25rem;font-size:.7rem;font-weight:600;display:grid}.trace-row{border-bottom:1px solid var(--border);grid-template-columns:1fr 2fr 1fr;gap:1rem;padding:.75rem 1.25rem;font-family:JetBrains Mono,monospace;font-size:.82rem;transition:background .15s;display:grid}.trace-row:last-child{border-bottom:none}.trace-row:hover{background:var(--surface2)}.trace-row .step-col{color:var(--muted)}.trace-row .action-col{color:var(--text)}.trace-row .state-col{color:#6366f1;font-weight:600}.code-block{border:1px solid var(--border);border-radius:var(--radius);background:#0d0d14;margin-bottom:1.5rem;overflow:hidden}.code-header{background:var(--surface2);border-bottom:1px solid var(--border);justify-content:space-between;align-items:center;padding:.6rem 1.25rem;display:flex}.code-lang{color:var(--muted);text-transform:uppercase;letter-spacing:1px;font-size:.75rem;font-weight:600}.copy-btn{border:1px solid var(--border);color:var(--muted);cursor:pointer;background:0 0;border-radius:6px;padding:3px 10px;font-size:.75rem;transition:color .2s,border-color .2s}.copy-btn:hover{color:#fff;border-color:var(--muted)}.copy-btn.copied{color:#22c55e;border-color:#22c55e4d}pre{color:#e2e8f0;padding:1.25rem;font-family:JetBrains Mono,monospace;font-size:.85rem;line-height:1.7;overflow-x:auto}.kw{color:#c792ea}.fn{color:#82aaff}.str{color:#c3e88d}.cmt{color:#546e7a;font-style:italic}.nm{color:#f78c6c}.op{color:#89ddff}.cls{color:#ffcb6b}.visual-box{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);margin-bottom:1.5rem;padding:1.5rem;overflow:hidden}.cell-row{flex-wrap:wrap;justify-content:center;align-items:flex-end;gap:4px;display:flex}.cell{border:2px solid var(--border);min-width:34px;height:34px;color:var(--muted);border-radius:6px;justify-content:center;align-items:center;font-family:JetBrains Mono,monospace;font-size:.82rem;font-weight:600;transition:all .3s;display:flex}.cell.seen{color:#a78bfa;background:#6366f11f;border-color:#6366f1}.cell.current{color:#f59e0b;background:#f59e0b2e;border-color:#f59e0b}.cell.window{color:#f59e0b;background:#f59e0b1f;border-color:#f59e0b}.cell.left-ptr{color:#10b981;background:#10b9811f;border-color:#10b981}.cell.right-ptr{color:#a78bfa;background:#6366f11f;border-color:#6366f1}.cell.match{color:#22c55e;background:#22c55e26;border-color:#22c55e}.cell.mid{color:#fbbf24;background:#f59e0b33;border-color:#f59e0b}.cell.out{opacity:.2}.cell.highlight{color:#ec4899;background:#ec48991f;border-color:#ec4899}.stack-column{flex-direction:column;justify-content:flex-end;align-items:center;gap:3px;min-height:100px;display:flex}.stack-item{color:#ef4444;background:#ef44441a;border:2px solid #ef4444;border-radius:6px;justify-content:center;align-items:center;width:110px;height:32px;font-family:JetBrains Mono,monospace;font-size:.8rem;font-weight:600;display:flex}.stack-item.top{color:#fb923c;background:#f9731626;border-color:#f97316}.stack-top-label{color:#f97316;margin-top:2px;font-size:.65rem;font-weight:600}.tree-row{justify-content:center;gap:10px;margin-bottom:8px;display:flex}.t-node{color:#22c55e;background:#22c55e1a;border:2px solid #22c55e;border-radius:50%;justify-content:center;align-items:center;width:36px;height:36px;font-family:JetBrains Mono,monospace;font-size:.78rem;font-weight:600;transition:all .3s;display:flex}.t-node.visited{color:#a78bfa;background:#6366f12e;border-color:#6366f1}.t-node.active{background:#22c55e4d;transform:scale(1.12)}.t-null{width:36px;height:36px;color:var(--border);justify-content:center;align-items:center;font-size:.65rem;display:flex}.graph-wrapper{height:150px;position:relative}.g-node{color:#14b8a6;background:#14b8a61a;border:2px solid #14b8a6;border-radius:50%;justify-content:center;align-items:center;width:36px;height:36px;font-family:JetBrains Mono,monospace;font-size:.78rem;font-weight:600;transition:all .3s;display:flex;position:absolute}.g-node.visited{color:#a78bfa;background:#6366f133;border-color:#6366f1}.dp-grid{overflow-x:auto}.dp-table{border-collapse:collapse;margin:0 auto;font-family:JetBrains Mono,monospace;font-size:.78rem}.dp-table td,.dp-table th{border:1px solid var(--border);text-align:center;width:30px;height:30px}.dp-table th{color:var(--muted);background:var(--surface2);font-size:.65rem}.dp-table .filled{color:#c4b5fd;background:#a855f71f;border-color:#a855f740}.dp-table .cur{color:#fff;background:#a855f759;border-color:#a855f7}.iv-wrapper{padding:.5rem 0}.iv-row{height:28px;margin-bottom:6px;position:relative}.iv-bar{border-radius:4px;align-items:center;height:22px;padding:0 6px;font-family:JetBrains Mono,monospace;font-size:.7rem;font-weight:600;display:flex;position:absolute}.bit-row{flex-wrap:wrap;justify-content:center;gap:2px;display:flex}.bit{border:1px solid var(--border);border-radius:4px;justify-content:center;align-items:center;width:28px;height:28px;font-family:JetBrains Mono,monospace;font-size:.8rem;font-weight:600;display:flex}.bit.one{color:#a78bfa;background:#6366f133;border-color:#6366f1}.bit.zero{color:var(--muted)}.ptr-label{text-align:center;margin-top:3px;font-family:JetBrains Mono,monospace;font-size:.6rem;font-weight:700}@keyframes fadeIn{0%{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}@keyframes slideDown{0%{opacity:0;transform:translateY(-6px)}to{opacity:1;transform:translateY(0)}}.fade-in{animation:.4s forwards fadeIn}.code-header-actions{align-items:center;gap:6px;display:flex}.run-btn{color:#a78bfa;cursor:pointer;background:#6366f11f;border:1px solid #6366f14d;border-radius:6px;padding:3px 10px;font-size:.75rem;font-weight:600;transition:background .2s,border-color .2s}.run-btn:hover{background:#6366f140;border-color:#6366f180}.run-btn.active{background:#6366f133;border-color:#6366f180}.code-editor-main{color:#e2e8f0;border:none;border-bottom:1px solid var(--border);resize:none;tab-size:4;caret-color:#a78bfa;box-sizing:border-box;background:#0d0d14;outline:none;width:100%;min-height:120px;padding:1.25rem;font-family:JetBrains Mono,monospace;font-size:.85rem;line-height:1.7;display:block;overflow:hidden}.code-editor-main:focus{background:#0e0e1a}.close-run-btn{border:1px solid var(--border);color:var(--muted);cursor:pointer;background:0 0;border-radius:6px;justify-content:center;align-items:center;width:26px;height:26px;padding:0;font-size:.8rem;transition:color .2s,border-color .2s;display:flex}.close-run-btn:hover{color:#fff;border-color:var(--muted)}.exec-btn{color:#a78bfa;cursor:pointer;white-space:nowrap;background:#6366f12e;border:1px solid #6366f166;border-radius:6px;padding:4px 14px;font-size:.78rem;font-weight:600;transition:background .2s}.exec-btn:hover:not(:disabled){background:#6366f152}.exec-btn.running,.exec-btn:disabled{opacity:.65;cursor:default}.output-panel{border-top:1px solid var(--border);background:#06060c}.output-panel.output-error{background:#ef444408;border-top-color:#ef44444d}.output-label{text-transform:uppercase;letter-spacing:1px;color:var(--muted);background:var(--surface2);border-bottom:1px solid var(--border);padding:.4rem 1.25rem;font-size:.7rem;font-weight:600}.output-panel.output-error .output-label{color:#f87171}.output-pre{color:#6ee7b7;white-space:pre-wrap;word-break:break-word;margin:0;padding:1rem 1.25rem;font-family:JetBrains Mono,monospace;font-size:.82rem;line-height:1.65}.output-panel.output-error .output-pre{color:#fca5a5}.output-hint{color:var(--muted);border-top:1px solid var(--border);padding:.75rem 1.25rem;font-size:.78rem}.output-hint code{background:var(--surface2);border:1px solid var(--border);color:#a78bfa;border-radius:4px;padding:1px 5px;font-family:JetBrains Mono,monospace;font-size:.78rem}.home-section-divider{align-items:center;gap:1rem;margin:3rem 0 1.5rem;display:flex}.home-section-line{background:var(--border);flex:1;height:1px}.home-section-title{text-transform:uppercase;letter-spacing:2px;color:var(--muted);white-space:nowrap;font-size:.75rem;font-weight:700}.py-home-banner{border-radius:var(--radius);background:linear-gradient(135deg,#10b98114,#3b82f60f);border:1px solid #10b98140;flex-wrap:wrap;justify-content:space-between;align-items:center;gap:1rem;margin-bottom:1rem;padding:1.25rem 1.5rem;display:flex}.py-banner-left{align-items:center;gap:1rem;display:flex}.py-banner-icon{font-size:2rem}.py-banner-title{color:#fff;margin-bottom:.25rem;font-size:1rem;font-weight:700}.py-banner-sub{color:var(--muted);font-size:.82rem}.py-banner-btn{color:#10b981;white-space:nowrap;background:#10b98126;border:1px solid #10b98159;border-radius:8px;padding:8px 18px;font-size:.85rem;font-weight:600;text-decoration:none;transition:background .2s}.py-banner-btn:hover{background:#10b98140}.py-level-badge{white-space:nowrap;border-radius:20px;padding:2px 8px;font-size:.7rem;font-weight:600}.py-topic-count{color:var(--muted);border-top:1px solid var(--border);margin-top:.75rem;padding-top:.75rem;font-size:.72rem}.py-level-legend{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);align-items:center;gap:.75rem;margin-bottom:2rem;padding:.85rem 1.25rem;display:flex}.py-legend-label{color:var(--muted);text-transform:uppercase;letter-spacing:1px;white-space:nowrap;font-size:.72rem;font-weight:600}.py-legend-end{color:#10b981;white-space:nowrap;font-family:JetBrains Mono,monospace;font-size:.72rem;font-weight:700}.py-level-bar{background:var(--border);border-radius:3px;flex:1;height:6px;overflow:hidden}.py-level-fill{background:linear-gradient(90deg,#10b981,#3b82f6);border-radius:3px;width:80%;height:100%}.go-banner{background:linear-gradient(135deg,#00add814,#5dc9e20f);border-color:#00add840}.go-banner-btn{color:#00add8;background:#00add826;border:1px solid #00add859}.go-banner-btn:hover{background:#00add840}@media (width<=768px){.home,.category-page,.problem-page{padding:1rem}.hero h1{font-size:2rem}.category-grid,.problems-grid{grid-template-columns:1fr}.trace-header,.trace-row{grid-template-columns:1fr 2fr}.trace-header span:last-child,.trace-row span:last-child{display:none}.py-home-banner{flex-direction:column;align-items:flex-start}}