/* ============================================================
   base.css —— 重置、排版、背景纹理、通用工具类
   ============================================================ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

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

body {
  font-family: var(--font);
  font-size: var(--fs-body);
  line-height: 1.68;
  color: var(--ink);
  background: var(--surface-alt);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

/* 全局渐变光晕（固定层，不参与滚动） */
body::before {
  content: ""; position: fixed; inset: 0; z-index: -1; pointer-events: none;
  background:
    radial-gradient(900px 500px at 78% -8%, rgba(18,183,106,.13), transparent 65%),
    radial-gradient(760px 460px at 6% 8%,  rgba(14,165,233,.10), transparent 62%),
    radial-gradient(900px 600px at 50% 110%, rgba(245,158,11,.08), transparent 60%);
}
/* 极淡网格纹理 */
body::after {
  content: ""; position: fixed; inset: 0; z-index: -2; pointer-events: none; opacity: .5;
  background-image:
    linear-gradient(rgba(13,31,22,.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(13,31,22,.035) 1px, transparent 1px);
  background-size: 56px 56px;
  mask-image: radial-gradient(circle at 50% 30%, #000 0%, transparent 78%);
  -webkit-mask-image: radial-gradient(circle at 50% 30%, #000 0%, transparent 78%);
}

a { color: inherit; text-decoration: none; }
button { font: inherit; border: 0; background: none; cursor: pointer; color: inherit; }
img, svg { display: block; max-width: 100%; }
ul { list-style: none; }
input, textarea { font: inherit; }
::selection { background: var(--brand); color: #fff; }

/* —— 标题 —— */
h1, h2, h3, h4 { line-height: 1.24; font-weight: 800; letter-spacing: -.6px; }
h1 { font-size: var(--fs-display); }
h2 { font-size: var(--fs-h2); }
h3 { font-size: var(--fs-h3); letter-spacing: -.3px; }
h4 { font-size: 15px; letter-spacing: -.2px; }

/* —— 文本工具 —— */
.lead { font-size: var(--fs-lead); color: var(--muted); max-width: 660px; margin-top: var(--sp-3); }
.muted { color: var(--muted); }
.mono  { font-family: var(--font-mono); }
.hl    { color: var(--brand-dark); }
/* 荧光笔标记 */
.mark {
  background: linear-gradient(180deg, transparent 62%, rgba(18,183,106,.28) 62%);
  padding: 0 3px;
}

/* —— 布局工具 —— */
.wrap { width: min(var(--wrap), 92vw); margin-inline: auto; }
.stack { display: flex; flex-direction: column; }
.row   { display: flex; align-items: center; }
.gap-1 { gap: var(--sp-1); } .gap-2 { gap: var(--sp-2); }
.gap-3 { gap: var(--sp-3); } .gap-4 { gap: var(--sp-4); }

/* —— 图标 —— */
.ico { width: 20px; height: 20px; flex: none; }
.ico-sm { width: 15px; height: 15px; flex: none; }
.ico-lg { width: 24px; height: 24px; flex: none; }

/* —— 入场动画（由 motion.js 添加 .in） —— */
.reveal {
  opacity: 0; transform: translateY(26px);
  transition: opacity .7s var(--ease), transform .7s var(--ease);
}
.reveal.in { opacity: 1; transform: none; }

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