:root {
  --bg: #ffffff;
  --fg: #111111;
  --muted: #6f6f6f;
  --line: #e7e7e7;
  --card: #ffffff;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0d0d0d;
    --fg: #f2f2f2;
    --muted: #9b9b9b;
    --line: #242424;
    --card: #121212;
  }
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

.wrap {
  max-width: 920px;
  margin: 0 auto;
  padding: 0 24px;
}

/* 顶栏 */
.top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 28px 0;
}

.brand {
  font-size: 15px;
  font-weight: 600;
  letter-spacing: 0.12em;
}

nav {
  display: flex;
  gap: 26px;
}

nav a {
  font-size: 13px;
  color: var(--muted);
  transition: color 0.15s ease;
}

nav a:hover {
  color: var(--fg);
}

/* 首屏 */
.hero {
  padding: clamp(56px, 13vh, 132px) 0 clamp(52px, 9vh, 96px);
}

.eyebrow {
  margin: 0 0 18px;
  font-size: 11px;
  letter-spacing: 0.22em;
  color: var(--muted);
}

h1 {
  margin: 0 0 22px;
  font-size: clamp(32px, 5.4vw, 54px);
  font-weight: 600;
  line-height: 1.24;
  letter-spacing: -0.02em;
}

.lede {
  max-width: 32em;
  margin: 0;
  font-size: 15px;
  line-height: 1.9;
  color: var(--muted);
}

/* 工具区 */
#tools {
  padding-bottom: 88px;
}

.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  padding-top: 22px;
  border-top: 1px solid var(--line);
}

.section-head h2 {
  margin: 0;
  font-size: 12px;
  font-weight: 500;
  letter-spacing: 0.18em;
  color: var(--muted);
}

.count {
  font-size: 11px;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 14px;
  margin-top: 22px;
}

.card {
  display: flex;
  flex-direction: column;
  gap: 30px;
  padding: 22px 22px 20px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--card);
  transition: transform 0.18s ease, border-color 0.18s ease;
}

.card:hover {
  transform: translateY(-2px);
  border-color: var(--fg);
}

.card-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
}

.icon {
  width: 24px;
  height: 24px;
  color: var(--muted);
  transition: color 0.18s ease;
}

.card:hover .icon {
  color: var(--fg);
}

.arrow {
  font-size: 14px;
  color: var(--muted);
  opacity: 0;
  transform: translate(-3px, 3px);
  transition: opacity 0.18s ease, transform 0.18s ease;
}

.card:hover .arrow {
  opacity: 1;
  transform: translate(0, 0);
}

.card h3 {
  margin: 0 0 6px;
  font-size: 16px;
  font-weight: 500;
}

.card p {
  margin: 0;
  font-size: 13px;
  line-height: 1.7;
  color: var(--muted);
}

.url {
  margin-top: auto;
  font-size: 11px;
  letter-spacing: 0.04em;
  color: var(--muted);
}

/* 页脚 */
footer {
  display: flex;
  flex-wrap: wrap;
  gap: 12px 24px;
  justify-content: space-between;
  padding: 24px 0 40px;
  border-top: 1px solid var(--line);
  font-size: 12px;
  color: var(--muted);
}

footer a {
  transition: color 0.15s ease;
}

footer a:hover {
  color: var(--fg);
}

:focus-visible {
  outline: 2px solid var(--fg);
  outline-offset: 3px;
  border-radius: 4px;
}

@media (max-width: 520px) {
  .wrap {
    padding: 0 20px;
  }

  .top {
    padding: 22px 0;
  }

  nav {
    gap: 18px;
  }

  .grid {
    grid-template-columns: 1fr;
  }

  .card {
    gap: 24px;
  }
}

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

  * {
    transition: none !important;
  }
}

/* Shared visible scrollbar baseline. */
html { scrollbar-color: var(--muted) var(--bg); scrollbar-width: thin; }
*::-webkit-scrollbar { width: 9px; height: 9px; }
*::-webkit-scrollbar-track { background: var(--bg); }
*::-webkit-scrollbar-thumb { background: var(--muted); border: 3px solid var(--bg); border-radius: 9px; }
*::-webkit-scrollbar-thumb:hover { background: var(--fg); }