/* ============================================================
   base.css — 重置、排版、可访问性与动效降级
   ============================================================ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

body {
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--fs-base);
  line-height: 1.7;
  letter-spacing: 0.02em;
  -webkit-font-smoothing: antialiased;
}

img { display: block; max-width: 100%; height: auto; }
ul, ol { list-style: none; }
a { color: inherit; text-decoration: none; }
strong { font-weight: 700; }

h1, h2, h3 {
  font-family: var(--font-display);
  font-weight: 900;
  line-height: 1.1;
  letter-spacing: -0.02em;
}

/* 键盘焦点：2px 描边 + 2px 偏移，任何底色可见 */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* ---------- 编排好的入场序列：初始态（仅在 JS 可用时隐藏，无 JS 直接可见） ---------- */
.js .reveal {
  opacity: 0;
  transform: translateY(24px);
}

/* 首屏错峰：组间隔 80ms，共 7 组 */
@media (prefers-reduced-motion: no-preference) {
  .reveal-load {
    animation: rise var(--dur-slow) var(--ease-out) both;
    animation-delay: calc(var(--d, 0) * 80ms);
  }
}
@keyframes rise {
  from { opacity: 0; transform: translateY(28px); }
  to   { opacity: 1; transform: none; }
}

/* 滚动触发到位态（由 IntersectionObserver 添加 .in） */
@media (prefers-reduced-motion: no-preference) {
  .js .reveal.in {
    opacity: 1;
    transform: none;
    transition:
      opacity var(--dur-base) var(--ease-out),
      transform var(--dur-base) var(--ease-out);
  }
}
/* reduced-motion：一切动效直接呈现终态 */
@media (prefers-reduced-motion: reduce) {
  .js .reveal { opacity: 1; transform: none; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* 纸面噪点氛围层：SVG feTurbulence，透明度 4% */
.grain::after {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 1;
  opacity: 0.04;
  mix-blend-mode: overlay;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.8'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}