*,:before,:after{box-sizing:border-box;margin:0;padding:0}:root{--bg:#f8f9fb;--white:#fff;--text:#1e293b;--text-secondary:#64748b;--border:#e2e8f0;--accent:#6366f1;--accent-light:#eef2ff;--green:#10b981;--green-light:#ecfdf5;--red:#ef4444;--red-light:#fef2f2;--purple:#8b5cf6;--blue:#3b82f6;--blue-light:#eff6ff;--yellow:#f59e0b;--yellow-light:#fffbeb;--shadow:0 1px 3px #0000000f;--radius:16px;--radius-sm:10px;--radius-xs:8px;--mono:"JetBrains Mono",monospace}body{background:var(--bg);color:var(--text);-webkit-font-smoothing:antialiased;min-height:100vh;font-family:Inter,-apple-system,sans-serif}.container{max-width:900px;margin:0 auto;padding:0 24px 48px}header{padding:20px 0}header a{color:var(--text-secondary);font-size:.95rem;font-weight:600;text-decoration:none}header a:hover{color:var(--accent)}.page-hero{text-align:center;padding:16px 0 24px}.page-hero h1{letter-spacing:-.02em;margin-bottom:6px;font-size:1.8rem;font-weight:800}.page-hero p{color:var(--text-secondary);max-width:560px;margin:0 auto;font-size:1rem}.spec-note{color:var(--text-secondary);background:var(--white);border:1px solid var(--border);border-radius:20px;margin-top:10px;padding:4px 14px;font-size:.75rem;display:inline-block}.card{background:var(--white);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow);margin-bottom:16px;padding:24px}.card-header{align-items:center;gap:8px;margin-bottom:16px;display:flex}.card-header .icon{border-radius:8px;justify-content:center;align-items:center;width:28px;height:28px;font-size:.9rem;display:flex}.card-header h3{text-transform:uppercase;letter-spacing:.04em;font-size:.85rem;font-weight:700}.btn{border:1.5px solid var(--border);border-radius:var(--radius-xs);background:var(--white);color:var(--text);cursor:pointer;box-shadow:var(--shadow);align-items:center;gap:6px;padding:10px 18px;font-family:inherit;font-size:.88rem;font-weight:600;transition:all .15s;display:inline-flex}.btn:hover{border-color:var(--green);color:var(--green);transform:translateY(-1px)}.btn.primary{background:var(--green);border-color:var(--green);color:#fff}.btn.primary:hover{background:#059669}.btn.success{background:var(--green);border-color:var(--green);color:#fff}.form-select{background:var(--bg);border:1.5px solid var(--border);border-radius:var(--radius-xs);color:var(--text);appearance:none;cursor:pointer;background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%2364748b' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10z'/%3E%3C/svg%3E");background-position:right 10px center;background-repeat:no-repeat;padding:8px 30px 8px 12px;font-size:.9rem;font-weight:600}.editor{border-radius:var(--radius-xs);color:#e2e8f0;width:100%;height:150px;font-family:var(--mono);resize:vertical;background:#1e293b;border:1.5px solid #334155;padding:14px;font-size:.9rem;line-height:1.6}.editor:focus{border-color:var(--accent);outline:none}.block-area{background:var(--bg);border:2px dashed var(--border);border-radius:var(--radius-sm);flex-direction:column;gap:4px;min-height:120px;padding:8px;transition:border-color .2s;display:flex}.block-area.over{border-color:var(--accent);background:var(--accent-light)}.code-block{background:var(--white);border:2px solid var(--border);border-radius:var(--radius-xs);font-family:var(--mono);cursor:grab;-webkit-user-select:none;user-select:none;align-items:center;gap:8px;padding:10px 16px;font-size:.9rem;transition:all .2s;display:flex}.code-block:active{cursor:grabbing;transform:scale(1.02);box-shadow:0 4px 12px #0000001a}.code-block .drag-handle{color:var(--text-secondary);font-size:.9rem}.code-block.correct{border-color:var(--green);background:var(--green-light)}.code-block.wrong{border-color:var(--red);background:var(--red-light);animation:.3s shake}.code-block .indent-marker{text-align:center;width:24px;min-width:24px;color:var(--text-secondary);opacity:.5;font-size:.7rem;display:inline-block}@keyframes shake{0%,to{transform:translate(0)}25%{transform:translate(-4px)}75%{transform:translate(4px)}}.problem-desc{color:var(--text-secondary);margin-bottom:12px;font-size:.88rem;line-height:1.6}.feedback{border-radius:var(--radius-sm);text-align:center;margin-top:12px;padding:16px;font-size:1rem;font-weight:600}.feedback.success{background:var(--green-light);color:var(--green)}.feedback.fail{background:var(--red-light);color:var(--red)}.controls{flex-wrap:wrap;align-items:center;gap:8px;margin-bottom:12px;display:flex}.tabs{border-bottom:2px solid var(--border);gap:4px;margin-bottom:20px;display:flex}.tab{color:var(--text-secondary);cursor:pointer;border-bottom:2px solid #0000;margin-bottom:-2px;padding:10px 18px;font-size:.88rem;font-weight:600;transition:all .15s}.tab:hover{color:var(--accent)}.tab.active{color:var(--accent);border-bottom-color:var(--accent)}.tab-content{display:none}.tab-content.active{display:block}