/* Top Byte 主站样式：纸面中性色加一个钴蓝强调色，系统字体，零脚本。 */
:root {
  --bg: #f5f4ef;
  --surface: #fbfaf6;
  --ink: #15171a;
  --ink-2: #4c5157;
  --ink-3: #7b8087;
  --line: #d9d6cc;
  --accent: #2748d8;
  --accent-ink: #1c36a8;
  --bit-off: #dcd9cf;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --mono: ui-monospace, "SF Mono", "Cascadia Mono", Menlo, Consolas, monospace;
  --wrap: 1080px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #101214;
    --surface: #16191c;
    --ink: #eceef0;
    --ink-2: #b3b9c0;
    --ink-3: #828991;
    --line: #2a2f35;
    --accent: #8fa6ff;
    --accent-ink: #b4c3ff;
    --bit-off: #2a2f35;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 24px; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
  text-rendering: optimizeLegibility;
}
::selection { background: var(--accent); color: #fff; }
a { color: var(--accent-ink); text-underline-offset: 3px; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
a:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 3px; }
.wrap { max-width: var(--wrap); margin: 0 auto; padding: 0 24px; }
.skip { position: absolute; left: -999px; top: 0; background: var(--ink); color: var(--bg); padding: 8px 14px; }
.skip:focus { left: 12px; top: 12px; z-index: 10; }

/* 页头 */
.site-head { border-bottom: 1px solid var(--line); }
.site-head .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; min-height: 64px; flex-wrap: wrap; }
.brand { display: inline-flex; align-items: center; gap: 12px; color: var(--ink); text-decoration: none; font-weight: 650; letter-spacing: .01em; }
.byte { display: inline-grid; grid-auto-flow: column; gap: 2px; }
.byte i { width: 7px; height: 14px; background: var(--bit-off); border-radius: 1px; }
/* 亮起的位与页面上的 0b0110_1110（十进制 110）对应 */
.byte i:nth-child(2), .byte i:nth-child(3), .byte i:nth-child(5), .byte i:nth-child(6), .byte i:nth-child(7) { background: var(--accent); }
.nav { display: flex; gap: 22px; flex-wrap: wrap; font-size: 15px; }
.nav a { color: var(--ink-2); text-decoration: none; padding: 6px 0; }
.nav a:hover, .nav a[aria-current="page"] { color: var(--ink); text-decoration: underline; }

/* 首屏 */
.hero { padding-top: 88px; padding-bottom: 72px; }
.hero .byte { gap: 6px; margin-bottom: 28px; }
.hero .byte i { width: 22px; height: 44px; border-radius: 3px; }
.bits { font-family: var(--mono); font-size: 13px; color: var(--ink-3); letter-spacing: .08em; margin: 0 0 20px; }
h1 { font-size: clamp(36px, 6vw, 64px); line-height: 1.06; letter-spacing: -.025em; margin: 0 0 22px; max-width: 16ch; font-weight: 680; text-wrap: balance; }
.lede { font-size: clamp(18px, 2vw, 21px); color: var(--ink-2); max-width: 38em; margin: 0; }

/* 分节 */
section { padding: 64px 0; border-top: 1px solid var(--line); }
.label { font-family: var(--mono); font-size: 12.5px; letter-spacing: .12em; text-transform: uppercase; color: var(--ink-3); margin: 0 0 14px; }
h2 { font-size: clamp(26px, 3.2vw, 36px); line-height: 1.15; letter-spacing: -.018em; margin: 0 0 14px; font-weight: 660; text-wrap: balance; }
h3 { font-size: 20px; line-height: 1.3; margin: 0 0 8px; font-weight: 650; }
p { margin: 0 0 16px; max-width: 42em; }
.intro { color: var(--ink-2); margin-bottom: 36px; }

/* 产品目录 */
.products { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 20px; list-style: none; padding: 0; margin: 0; }
.product { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 28px; display: flex; flex-direction: column; }
.product h3 { font-size: 26px; letter-spacing: -.01em; }
.product .kind { font-family: var(--mono); font-size: 12.5px; color: var(--accent-ink); letter-spacing: .06em; margin: 0 0 10px; }
.product p { color: var(--ink-2); }
.facts { margin: 4px 0 22px; padding: 0; font-size: 15px; }
.facts div { display: grid; grid-template-columns: 7.5em 1fr; gap: 12px; padding: 8px 0; border-top: 1px solid var(--line); }
.facts dt { color: var(--ink-3); }
.facts dd { margin: 0; }
.product .go { margin-top: auto; }
.btn { display: inline-block; background: var(--ink); color: var(--bg); text-decoration: none; padding: 11px 18px; border-radius: 9px; font-weight: 600; font-size: 15.5px; }
.btn:hover { background: var(--accent); color: #fff; text-decoration: none; }
@media (prefers-color-scheme: dark) { .btn:hover { color: #101214; } }

/* 原则 */
.principles { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 28px 36px; list-style: none; padding: 0; margin: 0; }
.principles li { border-top: 2px solid var(--ink); padding-top: 16px; }
.principles p { color: var(--ink-2); font-size: 16px; margin: 0; }

/* 问答 */
.faq { max-width: 46em; }
.faq div { padding: 20px 0; border-top: 1px solid var(--line); }
.faq dt { font-weight: 650; font-size: 18px; margin-bottom: 6px; }
.faq dd { margin: 0; color: var(--ink-2); }

/* 政策正文 */
.doc { padding: 56px 0 72px; }
.doc header { margin-bottom: 36px; }
.doc h1 { font-size: clamp(32px, 5vw, 48px); max-width: none; margin-bottom: 12px; }
.doc .meta { font-family: var(--mono); font-size: 13px; color: var(--ink-3); margin: 0; }
.doc .mirror { font-size: 14px; margin-top: 10px; color: var(--ink-3); }
.prose { max-width: 46em; }
.prose h2 { font-size: 24px; margin: 44px 0 12px; }
.prose h3 { margin: 28px 0 8px; }
.prose ul { padding-left: 1.3em; margin: 0 0 16px; max-width: 42em; }
.prose li { margin-bottom: 7px; }
.tbl { overflow-x: auto; margin: 18px 0 24px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); }
table { border-collapse: collapse; width: 100%; font-size: 15px; line-height: 1.5; min-width: 520px; }
th, td { text-align: left; padding: 10px 14px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { font-size: 13px; color: var(--ink-2); font-weight: 600; }
tr:last-child td { border-bottom: 0; }
code { font-family: var(--mono); font-size: .9em; }

/* 页脚 */
.site-foot { border-top: 1px solid var(--line); padding: 40px 0 56px; font-size: 15px; color: var(--ink-2); }
.site-foot .wrap { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 28px; }
.site-foot h2 { font-family: var(--mono); font-size: 12.5px; letter-spacing: .12em; text-transform: uppercase; color: var(--ink-3); margin: 0 0 10px; font-weight: 500; }
.site-foot ul { list-style: none; padding: 0; margin: 0; }
.site-foot li { margin-bottom: 6px; }
.site-foot a { color: var(--ink-2); }
.site-foot p { font-size: 14px; color: var(--ink-3); margin: 0; }

@media (max-width: 600px) {
  body { font-size: 16px; }
  .wrap { padding: 0 18px; }
  .hero { padding-top: 56px; padding-bottom: 48px; }
  .hero .byte i { width: 16px; height: 32px; }
  section { padding: 48px 0; }
  .product { padding: 22px; }
  .nav { gap: 16px; }
}
@media print {
  .site-head .nav, .skip { display: none; }
  body { background: #fff; }
}