/* ============ Base ============ */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: var(--font-body);
  font-size: var(--text-body);
  line-height: 1.75;
  color: var(--color-text-primary);
  background-color: var(--color-bg-primary);
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4, p {
  margin: 0;
}

/* 标题族·思源黑体：黑体笔画粗细均匀、字面饱满，
   比宋体需要更宽松的行高与更克制的中文字距，避免视觉过重。 */
h1, h2, h3 {
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.25;
}

h1 {
  font-size: var(--text-display);
  line-height: 1.3;
  letter-spacing: -0.015em;
}

h2 {
  font-size: var(--text-h2);
  letter-spacing: -0.005em;
}

h3 {
  font-size: var(--text-h3);
}

a {
  color: var(--color-accent);
  text-decoration: underline;
  text-decoration-color: transparent;
  text-underline-offset: 3px;
  transition: text-decoration-color var(--motion-fast) var(--ease-out);
}

a:hover {
  text-decoration-color: var(--color-accent);
}

img {
  max-width: 100%;
  display: block;
}

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

:focus:not(:focus-visible) {
  outline: none;
}

/* Skip link */
.skip-link {
  position: absolute;
  top: -48px;
  left: var(--space-4);
  z-index: 100;
  padding: var(--space-2) var(--space-4);
  background: var(--color-accent);
  color: #fff;
  border-radius: var(--radius-sm);
  transition: top var(--motion-fast);
}

.skip-link:focus {
  top: var(--space-2);
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}