/* ===== CSS Variables / Theme ===== */
:root {
  --bg: #ffffff;
  --bg-secondary: #f5f5f5;
  --text: #1a1a1a;
  --text-secondary: #666666;
  --border: #e0e0e0;
  --accent: #0066ff;
  --accent-hover: #0052cc;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
}

[data-theme="dark"] {
  --bg: #0f0f0f;
  --bg-secondary: #1a1a1a;
  --text: #e5e5e5;
  --text-secondary: #999999;
  --border: #333333;
  --accent: #4d94ff;
  --accent-hover: #80b3ff;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
}

/* ===== Reset ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
}

/* ===== Navigation Bar ===== */
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 24px;
  border-bottom: 1px solid var(--border);
  background: var(--bg-secondary);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-brand {
  font-weight: 700;
  font-size: 16px;
  text-decoration: none;
  color: var(--text);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 16px;
  list-style: none;
}

.nav-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 14px;
  transition: color 0.2s;
}

.nav-links a:hover {
  color: var(--accent);
}

.theme-toggle {
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 4px 10px;
  cursor: pointer;
  font-size: 14px;
  color: var(--text);
}

/* ===== Main Content ===== */
.container {
  max-width: 800px;
  margin: 0 auto;
  padding: 32px 24px;
}

/* ===== Utility ===== */
.card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
}

button, input, select, textarea {
  font-family: inherit;
  font-size: inherit;
}