*,: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;--purple-light:#f5f3ff;--blue:#3b82f6;--blue-light:#eff6ff;--yellow:#f59e0b;--yellow-light:#fffbeb;--orange:#f97316;--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}.form-input{background:var(--bg);border:1.5px solid var(--border);border-radius:var(--radius-xs);color:var(--text);font-family:var(--mono);width:100px;padding:8px 12px;font-size:1rem;font-weight:600}.form-input:focus{border-color:var(--accent);outline:none}.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}.controls{flex-wrap:wrap;align-items:center;gap:8px;margin-bottom:16px;display:flex}.call-stack{background:var(--bg);border:1px solid var(--border);border-radius:var(--radius-sm);flex-direction:column-reverse;gap:4px;min-height:200px;padding:16px;display:flex}.stack-frame{border-radius:var(--radius-xs);font-family:var(--mono);opacity:0;padding:10px 16px;font-size:.88rem;font-weight:600;transition:all .4s;transform:translateY(-10px)}.stack-frame.visible{opacity:1;transform:translateY(0)}.stack-frame.calling{background:var(--green-light);color:var(--green);border:2px solid var(--accent)}.stack-frame.returning{background:var(--green-light);color:var(--green);border:2px solid var(--green)}.stack-frame.base{background:var(--yellow-light);color:var(--yellow);border:2px solid var(--yellow)}.code-display{border-radius:var(--radius-xs);font-family:var(--mono);color:#e2e8f0;background:#1e293b;margin-bottom:16px;padding:16px;font-size:.88rem;line-height:1.8}.code-display .highlight{background:#6366f14d;margin:0 -16px;padding:0 16px;display:block}.code-display .comment{color:#64748b}.step-info{color:var(--text-secondary);background:var(--bg);border:1px solid var(--border);border-radius:var(--radius-xs);min-height:40px;margin-top:12px;padding:12px;font-size:.88rem}