:root {
  --bg: #ffffff;
  --text: #1a1a1a;
  --muted: #666666;
  --border: #dddddd;
  --accent: #2c5f8a;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #121212;
    --text: #e8e8e8;
    --muted: #999999;
    --border: #333333;
    --accent: #6fa8dc;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text);
}

header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 20px;
  border-bottom: 1px solid var(--border);
}

header h1 {
  font-size: 18px;
  margin: 0;
}

nav a {
  color: var(--accent);
  text-decoration: none;
  margin-left: 16px;
}

nav a.active {
  font-weight: bold;
}

main {
  padding: 20px;
  max-width: 900px;
  margin: 0 auto;
}

.muted {
  color: var(--muted);
}

.tabs {
  margin-bottom: 10px;
}

.tab-btn {
  padding: 6px 14px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text);
  cursor: pointer;
}

.tab-btn.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}