CSS 格式化

:root {
  --brand: #38bdf8;
  --muted: #64748b
}

body {
  margin: 0;
  font-family: system-ui, sans-serif;
  color: #0f172a
}

.card {
  border: 1px solid #e2e8f0;
  border-radius: 16px;
  padding: 24px
}

.card h1 {
  color: var(--brand);
  font-size: 24px
}

/* 主标题 */
@media (max-width:640px) {
  .card {
    padding: 12px
  }
}