/* 重置与排版基线 */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; scroll-padding-top: calc(var(--head-h) + 16px); }
body {
  margin: 0;
  padding-top: var(--head-h);
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.7 var(--font-sans);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
img, video, canvas, svg { display: block; max-width: 100%; }
img { height: auto; }
a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: var(--ink); }
ul, ol { margin: 0; padding: 0; list-style: none; }
h1, h2, h3, h4, p, figure { margin: 0; }
button { font: inherit; color: inherit; background: none; border: 0; padding: 0; cursor: pointer; }
::selection { background: var(--accent); color: var(--accent-ink); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 2px; }

h1 { font-size: clamp(2.4rem, 6vw, 5.2rem); font-weight: 900; line-height: 1.02; letter-spacing: -0.02em; }
h2 { font-size: clamp(1.7rem, 3.6vw, 2.8rem); font-weight: 800; line-height: 1.15; letter-spacing: -0.01em; }
h3 { font-size: 1.2rem; font-weight: 700; line-height: 1.3; }
mark { background: none; color: var(--accent); }
.mark-fill { background: var(--accent); color: var(--accent-ink); padding: 0.02em 0.32em; border-radius: 3px; }
.mono { font-family: var(--font-mono); }
.lead { font-size: clamp(1.02rem, 1.35vw, 1.22rem); line-height: 1.75; color: var(--dim); max-width: 62ch; }
.kicker {
  display: flex; align-items: center; gap: 12px;
  font: 500 11px/1 var(--font-mono); letter-spacing: 0.22em; text-transform: uppercase; color: var(--dim);
  margin-bottom: 18px;
}
.kicker b { color: var(--accent); font-weight: 700; }
.kicker::after { content: ""; flex: 0 0 48px; height: 1px; background: linear-gradient(90deg, var(--accent), transparent); }
.crumb { font-size: 11px; letter-spacing: 0.16em; color: var(--faint); }
.crumb a { color: var(--dim); text-decoration: none; }
.crumb a:hover { color: var(--accent); }

/* 布局 */
.wrap { width: 100%; max-width: var(--wrap); margin: 0 auto; padding: 0 var(--gutter); }
.sec { padding-block: clamp(64px, 9vw, 120px); }
.sec-alt { background: var(--bg-2); border-top: 1px solid var(--line-2); border-bottom: 1px solid var(--line-2); }
.page-hero { padding-block: clamp(56px, 8vw, 104px) clamp(24px, 4vw, 48px); }
.page-hero h1 { max-width: 20ch; }
.page-hero .lead { margin-top: 20px; }
.sec-head { display: flex; flex-wrap: wrap; align-items: flex-end; justify-content: space-between; gap: 16px 32px; margin-bottom: clamp(32px, 4vw, 56px); }
.sec-head > .kicker { flex-basis: 100%; margin-bottom: 0; }
.sec-head h2 { max-width: 24ch; }
.sec-head .lead { flex-basis: 100%; }
.sec-head .more { font: 600 13px/1 var(--font-mono); letter-spacing: 0.12em; color: var(--dim); text-decoration: none; padding-bottom: 6px; border-bottom: 1px solid var(--line); }
.sec-head .more:hover { color: var(--accent); border-color: var(--accent); }
.grid-2 { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 24px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 24px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 24px; }
@media (max-width: 1023px) { .grid-3, .grid-4 { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
@media (max-width: 639px) { .grid-2, .grid-3, .grid-4 { grid-template-columns: minmax(0, 1fr); } }

/* 小元件 */
.led { display: inline-block; width: 8px; height: 8px; border-radius: 50%; background: var(--accent); box-shadow: 0 0 10px var(--accent); vertical-align: middle; }
.skip-link { position: absolute; left: -999px; top: 8px; z-index: 999; background: var(--accent); color: var(--accent-ink); padding: 8px 12px; border-radius: 4px; }
.skip-link:focus { left: 8px; }

/* 滚动显现：无 JS 时直接可见 */
.rv { opacity: 0; transform: translateY(18px); transition: opacity 0.7s var(--ease), transform 0.7s var(--ease); }
.rv.in, html:not(.js) .rv { opacity: 1; transform: none; }
[data-stagger] > .rv:nth-child(2) { transition-delay: 0.08s; }
[data-stagger] > .rv:nth-child(3) { transition-delay: 0.16s; }
[data-stagger] > .rv:nth-child(4) { transition-delay: 0.24s; }
[data-stagger] > .rv:nth-child(5) { transition-delay: 0.32s; }
[data-stagger] > .rv:nth-child(6) { transition-delay: 0.40s; }

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

/* 窄屏标题字号：避免 10 字标题在 390px 下拆成 9+1 */
@media (max-width: 480px) {
  h1 { font-size: clamp(1.8rem, 8.6vw, 2.4rem); }
}