:root {
  color-scheme: light;
  --ink: #1f2329;
  --muted: #646a73;
  --line: #e5e6eb;
  --surface: #ffffff;
  --surface-soft: #f5f6f8;
  --primary: #3370ff;
  --primary-hover: #245bdb;
  font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  color: var(--ink);
  background: var(--surface);
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; }

.site-header,
main,
footer {
  width: min(1120px, calc(100% - 48px));
  margin-inline: auto;
}

.site-header {
  height: 76px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--line);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: var(--ink);
  font-size: 18px;
  font-weight: 700;
  text-decoration: none;
}

.brand img {
  width: 36px;
  height: 36px;
  border-radius: 10px;
}

nav { display: flex; align-items: center; gap: 28px; }

nav a,
.back-link a,
footer a {
  color: var(--muted);
  text-underline-offset: 4px;
}

nav a { text-decoration: none; }
nav a:hover,
nav a[aria-current="page"],
.back-link a:hover,
footer a:hover { color: var(--ink); }

.hero {
  max-width: 820px;
  padding: 112px 0 88px;
}

.eyebrow {
  margin: 0 0 16px;
  color: var(--primary);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: .08em;
}

h1 {
  margin: 0;
  font-size: clamp(42px, 6vw, 72px);
  line-height: 1.08;
  letter-spacing: -.045em;
}

.hero-copy,
.content-heading > p:last-child {
  max-width: 700px;
  margin: 28px 0 0;
  color: var(--muted);
  font-size: 19px;
  line-height: 1.75;
}

.actions { display: flex; gap: 12px; margin-top: 36px; }

.button,
.copy-button {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0 20px;
  border: 1px solid transparent;
  border-radius: 8px;
  font: inherit;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
}

.button-primary { color: #fff; background: var(--primary); }
.button-primary:hover { background: var(--primary-hover); }
.button-secondary,
.copy-button { color: var(--ink); background: var(--surface); border-color: var(--line); }
.button-secondary:hover,
.copy-button:hover { background: var(--surface-soft); }

.feature-list {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.feature-list article { padding: 32px 32px 36px 0; }
.feature-list article + article { padding-left: 32px; border-left: 1px solid var(--line); }
.feature-index { color: #8f959e; font-size: 12px; font-weight: 700; }
.feature-list h2 { margin: 24px 0 10px; font-size: 20px; }
.feature-list p { margin: 0; color: var(--muted); line-height: 1.7; }

.content-page { max-width: 900px; padding: 88px 0 72px; }
.content-heading h1 { font-size: clamp(38px, 5vw, 60px); }

.support-panel {
  margin-top: 56px;
  padding: 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 32px;
  background: var(--surface-soft);
  border: 1px solid var(--line);
  border-radius: 10px;
}

.support-label { margin: 0 0 8px; color: var(--muted); font-size: 13px; }
.support-panel h2 { margin: 0; font-size: 28px; }
.support-panel div > p:last-child { margin: 10px 0 0; color: var(--muted); line-height: 1.65; }

.help-list { padding: 48px 0 24px; }
.help-list h2 { margin: 0 0 16px; font-size: 20px; }
.help-list ul { margin: 0; padding-left: 22px; color: var(--muted); line-height: 2; }
.back-link { margin: 24px 0 0; }

footer {
  min-height: 100px;
  padding: 28px 0;
  display: flex;
  justify-content: space-between;
  gap: 24px;
  color: var(--muted);
  font-size: 13px;
}

:focus-visible { outline: 3px solid rgba(51, 112, 255, .28); outline-offset: 3px; }

@media (max-width: 720px) {
  .site-header,
  main,
  footer { width: min(100% - 32px, 1120px); }
  .site-header { height: auto; min-height: 68px; gap: 16px; }
  .brand { font-size: 16px; }
  .brand img { width: 32px; height: 32px; }
  nav { gap: 16px; font-size: 14px; }
  .hero { padding: 72px 0 60px; }
  h1 { font-size: 42px; }
  .hero-copy,
  .content-heading > p:last-child { font-size: 17px; }
  .actions { align-items: stretch; flex-direction: column; }
  .feature-list { grid-template-columns: 1fr; }
  .feature-list article { padding: 28px 0; }
  .feature-list article + article { padding-left: 0; border-left: 0; border-top: 1px solid var(--line); }
  .content-page { padding-top: 64px; }
  .support-panel { align-items: stretch; flex-direction: column; }
  .copy-button { align-self: flex-start; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; }
}