/* ==========================================================================
   base.css —— 重置、排版、焦点、氛围层、动效降级
   ========================================================================== */

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

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

body {
  margin: 0;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-variant-numeric: tabular-nums;
  overflow-x: hidden;
}

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

a { color: inherit; text-decoration: none; }

button, input { font: inherit; color: inherit; }

/* ---- 排版 ---------------------------------------------------------------- */

h1, h2, h3, h4 {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 400;                 /* 展示字用字重而非粗细取胜 */
  letter-spacing: var(--tracking-tight);
  line-height: var(--leading-heading);
}

p { margin: 0; }

.display {
  font-family: var(--font-display);
  font-size: var(--text-display);
  line-height: var(--leading-display);
  letter-spacing: var(--tracking-display);
  font-weight: 400;
}

.eyebrow {
  font-family: var(--font-sans);
  font-size: var(--text-xs);
  letter-spacing: var(--tracking-wide);
  text-transform: uppercase;
  color: var(--color-faint);
  font-weight: 400;
}

.lede {
  font-size: var(--text-lg);
  color: var(--color-muted);
  line-height: 1.6;
  max-width: 46ch;
}

.prose { max-width: 62ch; color: var(--color-muted); }
.prose p + p { margin-top: var(--space-4); }

.zh { font-family: var(--font-display); letter-spacing: .18em; }

/* ---- 版心 ---------------------------------------------------------------- */

.shell {
  max-width: var(--measure);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.rule {
  height: 1px;
  background: var(--color-border);
  border: 0;
  margin: 0;
}

section { padding-block: var(--space-7); }

/* ---- 焦点与可达性 -------------------------------------------------------- */

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

.visually-hidden {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}

.skip-link {
  position: absolute; top: -100px; left: var(--space-4);
  background: var(--color-text); color: var(--color-bg);
  padding: var(--space-2) var(--space-3); z-index: 100;
  transition: top var(--dur-fast) var(--ease-out);
}
.skip-link:focus { top: var(--space-3); }

/* ---- 氛围层：纸纹颗粒 + 极淡的暖色径向，替代纯色平铺 ---------------------- */
/* 颗粒用 SVG feTurbulence 生成，透明度 4%，不抢内容。 */

/* ---- 层级：渐变(0) < 内容(2) < 纸纹(3) < 吸顶页头(20) -------------------- */
/* 显式定义叠放顺序，避免 fixed 伪元素意外盖住正文。 */

main, .site-footer { position: relative; z-index: 2; }

body::before {
  content: "";
  position: fixed; inset: 0;
  pointer-events: none;
  z-index: 3;
  opacity: .04;
  mix-blend-mode: multiply;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='240' height='240'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.85' numOctaves='3'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

body::after {
  content: "";
  position: fixed; inset: 0;
  pointer-events: none;
  z-index: 0;
  background:
    radial-gradient(52rem 34rem at 88% -8%, rgba(168, 64, 47, .055), transparent 62%),
    radial-gradient(46rem 30rem at 4% 12%, rgba(74, 93, 78, .055), transparent 60%);
}

/* ---- 入场与滚动揭示：一次编排好的序列，错峰 80ms ------------------------- */

.reveal {
  opacity: 0;
  transform: translateY(22px);
}
.reveal.is-in {
  opacity: 1;
  transform: none;
  transition:
    opacity var(--dur-slow) var(--ease-out),
    transform var(--dur-slow) var(--ease-out);
  transition-delay: var(--reveal-delay, 0ms);
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { opacity: 1; transform: none; transition: none; }
  *, *::before, *::after {
    animation-duration: .01ms !important;
    transition-duration: .01ms !important;
  }
}