/* Base styles and CSS variables for light/dark mode */
:root {
  --bg: #f8fafc;
  --fg: #222;
  --accent: #2563eb;
  --border-radius: 8px;
  --font-family: "Inter", system-ui, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #18181b;
    --fg: #f3f4f6;
    --accent: #60a5fa;
  }
}

body {
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-family);
  margin: 0;
  min-height: 100vh;
  transition: background 0.2s, color 0.2s;
}

h1 {
  font-size: 2.5rem;
  font-weight: 700;
  margin: 2rem 0 1.5rem 0;
  color: var(--accent);
  text-align: center;
}

main {
  max-width: 600px;
  margin: 0 auto;
  padding: 2rem;
  border-radius: var(--border-radius);
  background: rgba(255, 255, 255, 0.7);
  box-shadow: 0 2px 16px rgba(0, 0, 0, 0.07);
}
@media (prefers-color-scheme: dark) {
  main {
    background: rgba(24, 24, 27, 0.85);
    box-shadow: 0 2px 16px rgba(0, 0, 0, 0.25);
  }
}

/* Extensible utility classes */
.flex-center {
  display: flex;
  align-items: center;
  justify-content: center;
}
.btn {
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--border-radius);
  padding: 0.5em 1.25em;
  font-size: 1rem;
  cursor: pointer;
  transition: background 0.2s;
}
.btn:hover {
  background: #1d4ed8;
}
@media (prefers-color-scheme: dark) {
  .btn:hover {
    background: #3b82f6;
  }
}