:root {
  --color-bg: #0d0d0f;
  --color-surface: #18181b;
  --color-surface-2: #1f1f23;
  --color-border: #2e2e35;
  --color-hover: #26262c;
  --color-text: #e8e8ed;
  --color-muted: #9999a8;
  --color-focus-ring: #6b9fff;

  --spacing-xs: 8px;
  --spacing-sm: 12px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 48px;

  --radius-sm: 8px;
  --radius-md: 10px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  --font-stack: -apple-system, BlinkMacSystemFont, "Segoe UI", Arial, sans-serif;
}

/* ── LIGHT MODE TOKENS ── */
[data-theme="light"] {
  --color-bg: #ffffff;
  --color-surface: #ffffff;
  --color-surface-2: #f4f4f8;
  --color-border: #d0d0d8;
  --color-hover: #ececf2;
  --color-text: #111111;
  --color-muted: #444444;
  --color-focus-ring: #4a7cf6;
}

html {
  background: #0d0d0f;
}

body {
  font-family: var(--font-stack);
  margin: 0;
  padding: var(--spacing-lg);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.5;
  transition: background 0.2s, color 0.2s;
}

[data-theme="light"] html,
[data-theme="light"] body {
  background: #ffffff;
}

.shell {
  max-width: 1600px;
  margin: 0 auto;
  background: var(--color-surface);
  padding: var(--spacing-lg);
  border-radius: var(--radius-xl);
  transition: background 0.2s;
}

.nav {
  display: flex;
  gap: var(--spacing-sm);
  flex-wrap: wrap;
  margin-bottom: 20px;
  align-items: center;
}

.nav a {
  color: var(--color-text);
  text-decoration: none;
  background: var(--color-surface);
  padding: 10px 14px;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  transition: background 0.15s ease;
}

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

.nav a:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

/* ── DARK MODE TOGGLE BUTTON ── */
.theme-toggle {
  margin-left: auto;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 8px 12px;
  font-size: 18px;
  cursor: pointer;
  line-height: 1;
  color: var(--color-text);
  transition: background 0.15s;
  flex-shrink: 0;
}
.theme-toggle:hover { background: var(--color-hover); }

.tile {
  transition: background 0.15s ease;
}

.tile:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.card {
  transition: background 0.15s ease;
}

.card:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

a:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

button:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

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

/* Responsive — tablet */
@media (max-width: 768px) {
  body {
    padding: var(--spacing-sm);
  }

  .shell {
    padding: var(--spacing-md);
  }

  h1 {
    font-size: 36px;
  }

  .grid {
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  }
}

/* Responsive — mobile */
@media (max-width: 480px) {
  body {
    padding: var(--spacing-xs);
  }

  .shell {
    padding: var(--spacing-sm);
    border-radius: var(--radius-lg);
  }

  h1 {
    font-size: 28px;
  }

  .grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .nav a {
    font-size: 14px;
    padding: 8px 10px;
  }
}