:root {
  --bg: #fbfbfd;
  --fg: #17181c;
  --muted: #6b7280;
  --line: #e8e8ee;
  --card: #ffffff;
  --accent: #3563e9;
  --accent-weak: #eef2ff;
  --code-bg: #16181d;
  --code-fg: #e6e6e6;
  --radius: 14px;
  --max: 980px;
}

* { 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", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  font-size: 16px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

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

.wrap { max-width: var(--max); margin: 0 auto; padding: 0 22px; }

/* header */
.site-header {
  position: sticky; top: 0; z-index: 10;
  background: rgba(251, 251, 253, 0.86);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--line);
}
.site-header .wrap {
  display: flex; align-items: center; justify-content: space-between;
  height: 62px;
}
.brand {
  font-weight: 700; font-size: 17px; color: var(--fg); letter-spacing: 0.2px;
  white-space: nowrap;
}
.brand:hover { text-decoration: none; }
.brand .dot { color: var(--accent); }
nav { display: flex; gap: 22px; }
nav a { color: var(--muted); font-size: 15px; }
nav a:hover { color: var(--fg); text-decoration: none; }
nav a.active { color: var(--fg); font-weight: 600; }

/* hero */
.hero { padding: 84px 0 56px; max-width: 640px; }
.eyebrow {
  color: var(--accent); font-size: 13px; font-weight: 600;
  letter-spacing: 1.2px; text-transform: uppercase; margin: 0 0 14px;
}
.hero h1 { font-size: 44px; line-height: 1.2; margin: 0 0 18px; letter-spacing: -0.5px; }
.lead { color: var(--muted); font-size: 17px; margin: 0 0 30px; }
.actions { display: flex; gap: 12px; flex-wrap: wrap; }
.btn {
  display: inline-block; padding: 11px 22px; border-radius: 999px;
  background: var(--fg); color: #fff; font-size: 15px; font-weight: 500;
  border: 1px solid var(--fg);
}
.btn:hover { text-decoration: none; opacity: 0.88; }
.btn.ghost { background: transparent; color: var(--fg); }
.btn.ghost:hover { background: var(--card); }

/* sections */
.section { padding: 12px 0 46px; }
.section-head {
  display: flex; align-items: baseline; justify-content: space-between;
  margin-bottom: 18px;
}
.section-head h2 { font-size: 21px; margin: 0; letter-spacing: -0.2px; }
.section-head > a { font-size: 14px; }
.page-head { padding: 58px 0 30px; }
.page-head h1 { font-size: 36px; margin: 0 0 4px; letter-spacing: -0.4px; }

/* cards */
.grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.card {
  background: var(--card); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 20px 20px 18px;
  transition: transform 0.16s ease, box-shadow 0.16s ease;
}
.card:hover { transform: translateY(-2px); box-shadow: 0 10px 30px rgba(23, 24, 28, 0.06); }
.card .meta { color: var(--muted); font-size: 12.5px; letter-spacing: 0.3px; }
.card h3 { font-size: 17px; margin: 8px 0 8px; line-height: 1.45; }
.card h3 a { color: var(--fg); }
.card p { color: var(--muted); font-size: 14px; margin: 0; }
.card .more { display: inline-block; margin-top: 12px; font-size: 13.5px; }

/* service strip */
.about-strip {
  background: var(--card); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 28px; margin-bottom: 46px;
}
.about-strip h2 { margin: 0 0 12px; font-size: 20px; }
.service-list { margin: 0 0 12px; padding-left: 18px; }
.service-list li { margin: 5px 0; }
.muted { color: var(--muted); font-size: 14.5px; }

/* note page */
.note { max-width: 760px; padding: 54px 0 30px; }
.note .meta { color: var(--muted); font-size: 13px; }
.note h1 { font-size: 38px; line-height: 1.25; letter-spacing: -0.5px; margin: 10px 0 26px; }
.prose { font-size: 16.5px; }
.prose h2 { font-size: 24px; margin: 38px 0 12px; letter-spacing: -0.2px; }
.prose h3 { font-size: 19px; margin: 28px 0 10px; }
.prose p { margin: 14px 0; }
.prose ul, .prose ol { margin: 14px 0; padding-left: 22px; }
.prose li { margin: 6px 0; }
.prose blockquote {
  margin: 18px 0; padding: 10px 18px; border-left: 3px solid var(--accent);
  background: var(--accent-weak); border-radius: 0 8px 8px 0; color: #3d4250;
}
.prose blockquote p { margin: 0; }
.prose code {
  background: #f1f2f6; padding: 2px 6px; border-radius: 5px;
  font-size: 0.88em; font-family: ui-monospace, SFMono-Regular, "JetBrains Mono", Menlo, Consolas, monospace;
}
.prose pre {
  background: var(--code-bg); color: var(--code-fg); padding: 18px 20px;
  border-radius: 12px; overflow-x: auto; line-height: 1.6; font-size: 13.5px;
  margin: 18px 0;
}
.prose pre code { background: none; padding: 0; color: inherit; font-size: inherit; }
.prose img { max-width: 100%; border-radius: 10px; border: 1px solid var(--line); }
.prose hr { border: 0; border-top: 1px solid var(--line); margin: 34px 0; }
.table-wrap { overflow-x: auto; margin: 18px 0; }
.prose table { border-collapse: collapse; width: 100%; font-size: 14.5px; }
.prose th, .prose td { border: 1px solid var(--line); padding: 8px 12px; text-align: left; }
.prose th { background: #f6f7fa; font-weight: 600; }

.note-nav {
  display: flex; justify-content: space-between; gap: 20px;
  border-top: 1px solid var(--line); margin-top: 46px; padding-top: 20px; font-size: 14px;
}

/* about */
.about-grid { max-width: 720px; padding-bottom: 60px; }

/* footer */
.site-footer {
  border-top: 1px solid var(--line); margin-top: 20px; padding: 26px 0 40px;
  color: var(--muted); font-size: 13.5px;
}
.site-footer a { color: var(--muted); }
.site-footer a:hover { color: var(--accent); }

@media (max-width: 820px) {
  .grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 560px) {
  .grid { grid-template-columns: 1fr; }
  .hero { padding: 54px 0 34px; }
  .hero h1 { font-size: 32px; }
  .note h1 { font-size: 28px; }
  nav { gap: 14px; }
  nav a { font-size: 14px; }
  .site-header .wrap { height: 56px; }
}