:root {
  --bg: #0d1117;
  --surface: #161b22;
  --border: #30363d;
  --text: #e6edf3;
  --text-muted: #8b949e;
  --accent: #2da44e;
  --accent-hover: #2c974b;
  --danger: #f85149;
  --warning: #d29922;
  --info: #58a6ff;
  --radius: 6px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  font-size: 14px;
}

header {
  padding: 24px 32px;
  border-bottom: 1px solid var(--border);
}

header h1 {
  font-size: 24px;
  font-weight: 600;
}

.subtitle {
  color: var(--text-muted);
  font-size: 14px;
  margin-top: 4px;
}

nav {
  display: flex;
  gap: 4px;
  padding: 0 32px;
  border-bottom: 1px solid var(--border);
  background: var(--surface);
}

nav a {
  padding: 12px 16px;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 14px;
  border-bottom: 2px solid transparent;
  transition: color 0.15s, border-color 0.15s;
}

nav a:hover { color: var(--text); }
nav a.active {
  color: var(--text);
  border-bottom-color: var(--accent);
}

main { padding: 32px; max-width: 1400px; margin: 0 auto; }

.section { display: none; }
.section.active { display: block; }

h2 {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 16px;
  margin-top: 32px;
}
h2:first-child { margin-top: 0; }

/* Stats */
.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 16px;
  margin-bottom: 32px;
}

.stat-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  text-align: center;
}

.stat-number {
  display: block;
  font-size: 32px;
  font-weight: 700;
  color: var(--accent);
}

.stat-label {
  display: block;
  font-size: 12px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-top: 4px;
}

/* Category grid */
.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}

.category-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  cursor: pointer;
  transition: border-color 0.15s;
}

.category-card:hover { border-color: var(--accent); }

.category-card h3 {
  font-size: 16px;
  margin-bottom: 8px;
}

.category-stats, .category-scoring {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 4px;
}

.badge {
  padding: 2px 8px;
  border-radius: 12px;
  font-size: 11px;
  font-weight: 500;
}

.badge-easy { background: rgba(45,164,78,0.15); color: var(--accent); }
.badge-medium { background: rgba(210,153,34,0.15); color: var(--warning); }
.badge-hard { background: rgba(248,81,73,0.15); color: var(--danger); }

/* Model grid */
.model-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 16px;
}

.model-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
}

.model-card h4 {
  font-size: 15px;
  margin-bottom: 6px;
  color: var(--info);
}

.model-card p {
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.primitives {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.primitive-tag {
  background: rgba(88,166,255,0.1);
  color: var(--info);
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 11px;
  font-family: 'SF Mono', Consolas, monospace;
}

/* Task browser */
.task-browser {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 16px;
  min-height: 600px;
}

.task-list {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px;
  overflow-y: auto;
  max-height: 80vh;
}

.task-item {
  padding: 10px 12px;
  border-radius: 4px;
  cursor: pointer;
  margin-bottom: 4px;
  border: 1px solid transparent;
  transition: background 0.1s, border-color 0.1s;
}

.task-item:hover { background: rgba(255,255,255,0.03); }
.task-item.selected {
  background: rgba(45,164,78,0.1);
  border-color: var(--accent);
}

.task-item .task-id {
  font-family: 'SF Mono', Consolas, monospace;
  font-size: 12px;
  font-weight: 500;
}

.task-item .task-diff {
  font-size: 11px;
  color: var(--text-muted);
  margin-top: 2px;
}

.task-detail {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  overflow-y: auto;
  max-height: 80vh;
}

.placeholder {
  color: var(--text-muted);
  text-align: center;
  padding: 40px;
}

/* Task detail */
.task-detail h3 {
  font-size: 18px;
  margin-bottom: 4px;
}

.task-detail .meta {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
}

.task-detail .instruction {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 16px;
  font-family: 'SF Mono', Consolas, monospace;
  font-size: 13px;
  white-space: pre-wrap;
  margin-bottom: 16px;
  max-height: 400px;
  overflow-y: auto;
}

.analysis-box {
  background: rgba(88,166,255,0.05);
  border: 1px solid rgba(88,166,255,0.2);
  border-radius: 4px;
  padding: 16px;
  margin-bottom: 16px;
}

.analysis-box h4 {
  color: var(--info);
  font-size: 14px;
  margin-bottom: 8px;
}

.analysis-box ul {
  list-style: none;
  padding-left: 0;
}

.analysis-box li {
  font-size: 13px;
  color: var(--text-muted);
  padding: 2px 0;
}

.analysis-box li::before {
  content: "?";
  color: var(--info);
  margin-right: 8px;
}

.run-btn {
  background: var(--accent);
  color: white;
  border: none;
  padding: 10px 20px;
  border-radius: var(--radius);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s;
}

.run-btn:hover { background: var(--accent-hover); }
.run-btn:disabled { opacity: 0.5; cursor: wait; }

.result-box {
  margin-top: 16px;
  padding: 16px;
  border-radius: 4px;
  font-family: 'SF Mono', Consolas, monospace;
  font-size: 13px;
  display: none;
}

.result-box.success {
  background: rgba(45,164,78,0.1);
  border: 1px solid var(--accent);
  display: block;
}

.result-box.failure {
  background: rgba(248,81,73,0.1);
  border: 1px solid var(--danger);
  display: block;
}

.score-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  margin-top: 12px;
}

.score-cell {
  text-align: center;
  padding: 8px;
  background: var(--bg);
  border-radius: 4px;
}

.score-cell .label {
  font-size: 10px;
  color: var(--text-muted);
  text-transform: uppercase;
}

.score-cell .value {
  font-size: 18px;
  font-weight: 700;
}

/* Leaderboard */
.leaderboard-table {
  width: 100%;
  border-collapse: collapse;
}

.leaderboard-table th, .leaderboard-table td {
  padding: 10px 12px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.leaderboard-table th {
  font-size: 12px;
  text-transform: uppercase;
  color: var(--text-muted);
  letter-spacing: 0.5px;
}

.leaderboard-table tr:hover { background: rgba(255,255,255,0.02); }

footer {
  padding: 24px 32px;
  border-top: 1px solid var(--border);
  text-align: center;
  color: var(--text-muted);
  font-size: 12px;
}

footer a { color: var(--info); text-decoration: none; }