:root {
  --bg: #ffffff;
  --fg: #1a1a1a;
  --accent: #0b6bcb;
}

body.dark {
  --bg: #111111;
  --fg: #eeeeee;
  --accent: #5aa9ff;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: system-ui, sans-serif;
  line-height: 1.6;
  background: var(--bg);
  color: var(--fg);
}

header, main {
  max-width: 42rem;
  margin: 0 auto;
  padding: 1rem;
}

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

nav a {
  margin-left: 1rem;
  color: var(--accent);
  text-decoration: none;
}

nav a:hover { text-decoration: underline; }

button {
  padding: 0.5rem 1rem;
  border: 1px solid var(--accent);
  background: none;
  color: var(--accent);
  border-radius: 6px;
  cursor: pointer;
}