:root {
  color-scheme: light;
  --ink: #111820;
  --muted: #5f6b76;
  --line: #d9dfe5;
  --paper: #ffffff;
  --canvas: #eef1f4;
  --accent: #1677b8;
  --accent-dark: #0f5d91;
  font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; color: var(--ink); background: var(--canvas); line-height: 1.7; }
a { color: var(--accent-dark); text-underline-offset: 3px; }
a:hover { color: var(--accent); }

.shell { width: min(1080px, calc(100% - 32px)); margin: 24px auto 48px; }
.topbar { display: flex; align-items: center; justify-content: space-between; gap: 24px; padding: 14px 18px; border: 1px solid var(--line); border-radius: 16px 16px 0 0; background: #121b24; }
.brand { display: flex; align-items: center; gap: 11px; color: #fff; text-decoration: none; font-weight: 750; letter-spacing: -.01em; }
.mark { display: grid; width: 34px; height: 34px; place-items: center; border-radius: 9px; color: #111820; background: #fff; font: 800 13px/1 ui-monospace, SFMono-Regular, Menlo, monospace; }
.nav { display: flex; flex-wrap: wrap; gap: 18px; }
.nav a { color: #b8c2cc; font-size: 14px; text-decoration: none; }
.nav a[aria-current="page"], .nav a:hover { color: #fff; }

.paper { min-height: 640px; padding: clamp(34px, 7vw, 82px); border: 1px solid var(--line); border-top: 0; border-radius: 0 0 16px 16px; background: var(--paper); box-shadow: 0 24px 65px rgba(35, 49, 62, .09); }
.eyebrow { margin: 0 0 16px; color: var(--accent-dark); font: 700 12px/1.2 ui-monospace, SFMono-Regular, Menlo, monospace; letter-spacing: .12em; text-transform: uppercase; }
h1 { max-width: 820px; margin: 0; font-size: clamp(38px, 7vw, 76px); line-height: 1.06; letter-spacing: -.055em; }
.lead { max-width: 720px; margin: 26px 0 0; color: var(--muted); font-size: clamp(17px, 2.2vw, 21px); }
.actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 34px; }
.button { display: inline-flex; min-height: 46px; align-items: center; justify-content: center; padding: 0 18px; border: 1px solid var(--ink); border-radius: 9px; color: #fff; background: var(--ink); font-weight: 700; text-decoration: none; }
.button:hover { color: #fff; background: #283540; }
.button.secondary { color: var(--ink); background: #fff; }
.button.secondary:hover { color: var(--accent-dark); border-color: var(--accent-dark); }
.button:focus-visible, .nav a:focus-visible, a:focus-visible { outline: 3px solid rgba(22, 119, 184, .35); outline-offset: 3px; }

.rule { height: 1px; margin: 64px 0 42px; background: var(--line); }
.grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.feature { padding-top: 17px; border-top: 3px solid var(--ink); }
.feature code { color: var(--accent-dark); font-size: 12px; }
.feature h2 { margin: 10px 0 7px; font-size: 18px; }
.feature p { margin: 0; color: var(--muted); font-size: 14px; }

.prose { max-width: 760px; }
.prose h1 { font-size: clamp(34px, 6vw, 58px); }
.prose h2 { margin: 42px 0 10px; font-size: 22px; letter-spacing: -.02em; }
.prose p, .prose li { color: #3f4b56; }
.prose ul { padding-left: 22px; }
.notice { margin: 28px 0; padding: 18px 20px; border-left: 4px solid var(--accent); background: #edf7fd; }
.meta { margin-top: 18px; color: var(--muted); font-size: 13px; }
.footer { padding: 18px 4px 0; color: #697680; font-size: 12px; text-align: center; }

@media (max-width: 720px) {
  .shell { width: min(100% - 20px, 1080px); margin-top: 10px; }
  .topbar { align-items: flex-start; flex-direction: column; }
  .paper { padding: 34px 24px; }
  .grid { grid-template-columns: 1fr; }
  .rule { margin-top: 46px; }
}

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