:root {
  --bg: #ffffff;
  --bg-alt: #f6f8fb;
  --fg: #16191d;
  --fg-soft: #5b6472;
  --line: #e3e8ef;
  --accent: #2563eb;
  --accent-dark: #1d4ed8;
  --radius: 12px;
  --shadow: 0 1px 2px rgba(16, 24, 40, .05), 0 8px 24px rgba(16, 24, 40, .06);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
        "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent-dark); }

.wrap { width: 100%; max-width: 1080px; margin: 0 auto; padding: 0 24px; }
.wrap.narrow { max-width: 760px; }

/* ---------- header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(255, 255, 255, .88);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--line);
}

.header-inner {
  display: flex;
  align-items: center;
  gap: 28px;
  height: 64px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 9px;
  font-weight: 650;
  font-size: 17px;
  letter-spacing: -.01em;
  color: var(--fg);
}

.brand .mark { width: 26px; height: 26px; fill: var(--accent); }

.nav { display: flex; gap: 22px; margin-left: auto; }
.nav a { color: var(--fg-soft); font-size: 14.5px; }
.nav a:hover { color: var(--fg); }

.btn {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  padding: 11px 22px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
  color: var(--fg);
  font-weight: 600;
  transition: transform .12s ease, box-shadow .12s ease, background .12s ease;
}

.btn:hover { transform: translateY(-1px); box-shadow: var(--shadow); color: var(--fg); }

.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-dark); border-color: var(--accent-dark); color: #fff; }

.btn-sm { padding: 8px 16px; font-size: 14.5px; }

.btn .os { font-size: 15px; }
.btn .os-meta { font-size: 12px; font-weight: 450; opacity: .78; }

/* ---------- hero ---------- */
.hero {
  padding: 84px 0 72px;
  background:
    radial-gradient(900px 380px at 50% -60px, #eaf1ff 0%, rgba(234, 241, 255, 0) 70%),
    var(--bg);
  text-align: center;
  border-bottom: 1px solid var(--line);
}

.eyebrow {
  display: inline-block;
  margin: 0 0 18px;
  padding: 5px 13px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: #fff;
  color: var(--fg-soft);
  font-size: 13px;
}

.hero h1 {
  margin: 0 0 20px;
  font-size: clamp(30px, 5vw, 46px);
  line-height: 1.22;
  letter-spacing: -.02em;
  font-weight: 700;
}

.lede {
  max-width: 620px;
  margin: 0 auto 34px;
  color: var(--fg-soft);
  font-size: 17px;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  justify-content: center;
}

.checksums {
  margin: 22px 0 0;
  color: var(--fg-soft);
  font-size: 13.5px;
}

/* ---------- sections ---------- */
.section { padding: 76px 0; }
.section-alt { background: var(--bg-alt); border-block: 1px solid var(--line); }

.section-title {
  margin: 0 0 34px;
  font-size: 27px;
  letter-spacing: -.015em;
  font-weight: 680;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 18px;
}

.card {
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
}

.card h3 { margin: 0 0 9px; font-size: 16.5px; font-weight: 640; }
.card p { margin: 0; color: var(--fg-soft); font-size: 14.5px; }

/* ---------- changelog ---------- */
.entry { margin-bottom: 30px; }
.entry:last-child { margin-bottom: 0; }
.entry h3 { margin: 0 0 4px; font-size: 17px; font-weight: 640; }
.entry .meta { margin: 0 0 12px; color: var(--fg-soft); font-size: 13.5px; }
.entry ul { margin: 0; padding-left: 20px; color: var(--fg-soft); font-size: 14.5px; }
.entry li { margin-bottom: 5px; }

.tag {
  display: inline-block;
  margin-left: 7px;
  padding: 2px 8px;
  border-radius: 999px;
  background: #eef2f7;
  color: var(--fg-soft);
  font-size: 12px;
  font-weight: 550;
  vertical-align: 2px;
}

.tag-new { background: #dcfce7; color: #15803d; }

/* ---------- faq ---------- */
details {
  padding: 15px 0;
  border-bottom: 1px solid var(--line);
}

summary {
  cursor: pointer;
  font-weight: 600;
  font-size: 15.5px;
  list-style: none;
}

summary::-webkit-details-marker { display: none; }
summary::before { content: "▸ "; color: var(--fg-soft); }
details[open] summary::before { content: "▾ "; }

details p { margin: 10px 0 0; color: var(--fg-soft); font-size: 14.5px; }
code { padding: 2px 6px; border-radius: 5px; background: #eef2f7; font-size: 13.5px; }

/* ---------- footer ---------- */
.site-footer { padding: 34px 0; border-top: 1px solid var(--line); }

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  align-items: center;
  justify-content: space-between;
  color: var(--fg-soft);
  font-size: 13.5px;
}

.footer-inner p { margin: 0; }
.footer-inner nav { display: flex; gap: 18px; }
.footer-inner a { color: var(--fg-soft); }

@media (max-width: 720px) {
  .nav { display: none; }
  .header-inner { gap: 16px; }
  .hero { padding: 56px 0 48px; }
  .cta-row .btn { width: 100%; }
}