/* 线路设计蓝图 — one stylesheet, no web fonts, nothing loaded from elsewhere.
   The look follows the app: drafting paper, ink, one amber accent, hairlines instead of boxes. */
:root {
  --paper: #f4f1e7;
  --sheet: #fbfaf3;
  --ink: #183c36;
  --soft: #526a64;
  --line: #183c3630;
  --hair: #183c361a;
  --accent: #e8bd6b;
  --accent-ink: #3b2c08;
  --teal: #246a5d;
  --sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", "Source Han Sans SC", system-ui, sans-serif;
  --mono: "SF Mono", "JetBrains Mono", Menlo, Consolas, "Roboto Mono", monospace;
  --measure: 68ch;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --paper: #10201d;
    --sheet: #162a26;
    --ink: #e9efe6;
    --soft: #a5b8b1;
    --line: #e9efe640;
    --hair: #e9efe61f;
    --accent: #e8bd6b;
    --accent-ink: #2a1f05;
    --teal: #7fd0bd;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
body {
  margin: 0; background: var(--paper); color: var(--ink);
  font: 16px/1.75 var(--sans); text-rendering: optimizeLegibility;
  /* the faint drafting grid of the app's start page */
  background-image: linear-gradient(var(--hair) 1px, transparent 1px), linear-gradient(90deg, var(--hair) 1px, transparent 1px);
  background-size: 48px 48px; background-position: -1px -1px;
}
img { max-width: 100%; height: auto; display: block; }
a { color: var(--teal); text-underline-offset: 3px; }
a:hover { color: var(--ink); }
.skip { position: absolute; left: -999px; }
.skip:focus { left: 16px; top: 12px; background: var(--sheet); padding: 6px 12px; z-index: 5; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }

/* ---------- header ---------- */
.top {
  display: flex; align-items: center; justify-content: space-between; gap: 16px 32px; flex-wrap: wrap;
  max-width: 1160px; margin: 0 auto; padding: 18px 24px;
}
.brand { display: inline-flex; align-items: center; gap: 12px; color: var(--ink); text-decoration: none; font-weight: 600; font-size: 19px; letter-spacing: .02em; }
.brand img { border-radius: 7px; }
.top nav { display: flex; flex-wrap: wrap; gap: 4px 6px; }
.top nav a { color: var(--soft); text-decoration: none; padding: 6px 12px; border-radius: 7px; font-size: 15px; }
.top nav a:hover { color: var(--ink); background: var(--hair); }
.top nav a[aria-current="page"] { color: var(--accent-ink); background: var(--accent); font-weight: 600; }

/* ---------- page frame ---------- */
main { max-width: 1160px; margin: 0 auto; padding: 8px 24px 72px; }
.sheet {
  position: relative; background: var(--sheet); border: 1px solid var(--line); padding: 44px 48px;
  margin: 12px 0 0;
}
/* the inner frame line and corner ticks of a drawing sheet */
.sheet::before { content: ""; position: absolute; inset: 8px; border: 1px solid var(--hair); pointer-events: none; }
.kicker { font: 500 12px/1.4 var(--mono); letter-spacing: .14em; text-transform: uppercase; color: var(--soft); margin: 0 0 18px; }
h1 { font-size: clamp(30px, 4.6vw, 50px); line-height: 1.18; margin: 0 0 18px; font-weight: 650; letter-spacing: -.01em; text-wrap: balance; }
h2 { font-size: 25px; line-height: 1.3; margin: 0 0 8px; font-weight: 650; }
h3 { font-size: 17px; line-height: 1.45; margin: 0 0 4px; font-weight: 650; }
p { margin: 0 0 14px; }
.lede { font-size: 18px; color: var(--soft); max-width: var(--measure); }
.prose { max-width: var(--measure); }
.prose h2 { margin-top: 44px; }
.prose h3 { margin-top: 26px; }
.prose ul, .prose ol { padding-left: 1.3em; margin: 0 0 16px; }
.prose li { margin-bottom: 6px; }
.note { color: var(--soft); font-size: 14.5px; }
.draft { display: inline-block; font: 600 12px/1 var(--mono); letter-spacing: .1em; padding: 6px 10px; border: 1px solid var(--line); color: var(--soft); margin-bottom: 18px; }
section { margin-top: 64px; }
.section-head { display: flex; align-items: baseline; gap: 16px; border-top: 1px solid var(--line); padding-top: 14px; margin-bottom: 26px; flex-wrap: wrap; }
.section-head .no { font: 500 12px/1 var(--mono); letter-spacing: .12em; color: var(--soft); }
.section-head p { margin: 0; color: var(--soft); flex-basis: 100%; max-width: var(--measure); }

/* ---------- buttons ---------- */
.actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 26px; }
.button { display: inline-flex; align-items: center; min-height: 44px; padding: 0 22px; border-radius: 8px; text-decoration: none; font-weight: 600; font-size: 15.5px; }
.button.primary { background: var(--accent); color: var(--accent-ink); }
.button.primary:hover { filter: brightness(1.06); color: var(--accent-ink); }
.button.ghost { color: var(--ink); background: var(--hair); }
.button.ghost:hover { background: var(--line); }
.button.disabled { color: var(--soft); background: var(--hair); cursor: default; }

/* ---------- hero ---------- */
.hero { display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 6fr); gap: 44px; align-items: center; }
figure { margin: 0; }
figure img { border: 1px solid var(--line); background: var(--paper); width: 100%; }
figcaption { font-size: 13px; color: var(--soft); margin-top: 8px; line-height: 1.55; }
.title-block { display: grid; grid-template-columns: repeat(4, auto); gap: 0; margin-top: 30px; border: 1px solid var(--line); width: fit-content; max-width: 100%; font: 12px/1.5 var(--mono); }
.title-block div { padding: 7px 14px; border-right: 1px solid var(--line); }
.title-block div:last-child { border-right: 0; }
.title-block b { display: block; font-weight: 500; color: var(--soft); letter-spacing: .08em; }

/* ---------- lists of things, ruled not boxed ---------- */
.steps { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 0 28px; counter-reset: step; }
.steps li { counter-increment: step; border-top: 2px solid var(--ink); padding-top: 14px; }
.steps li::before { content: "0" counter(step); font: 500 12px/1 var(--mono); letter-spacing: .12em; color: var(--soft); display: block; margin-bottom: 10px; }
.steps p { color: var(--soft); margin: 0; font-size: 15px; }
.kernel { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0 44px; }
.kernel div { border-top: 1px solid var(--line); padding: 16px 0 18px; }
.kernel p { margin: 0; color: var(--soft); font-size: 15px; }
.shots { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 36px 32px; }
.shots .wide { grid-column: 1 / -1; }
.plain { list-style: none; padding: 0; margin: 0; display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 0 32px; }
.plain li { border-top: 1px solid var(--line); padding: 14px 0 16px; color: var(--soft); font-size: 15px; }
.plain b { display: block; color: var(--ink); font-weight: 650; margin-bottom: 2px; }
table { border-collapse: collapse; width: 100%; font-size: 15px; margin: 8px 0 20px; }
th, td { text-align: left; padding: 9px 14px 9px 0; border-bottom: 1px solid var(--line); vertical-align: top; }
th { font-weight: 600; color: var(--soft); font-size: 13.5px; }
td.num, th.num { text-align: right; font-variant-numeric: tabular-nums; padding-right: 0; }
.table-wrap { overflow-x: auto; }
code, .mono { font: 13.5px/1.6 var(--mono); }
.log { list-style: none; padding: 0; margin: 0; }
.log > li { border-top: 1px solid var(--line); padding: 22px 0 10px; display: grid; grid-template-columns: 150px minmax(0, 1fr); gap: 0 28px; }
.log time { font: 500 13px/1.9 var(--mono); color: var(--soft); }

/* ---------- footer ---------- */
.foot { max-width: 1160px; margin: 0 auto; padding: 26px 24px 44px; border-top: 1px solid var(--line); font-size: 14px; color: var(--soft); }
.foot-row { display: flex; justify-content: space-between; gap: 12px 28px; flex-wrap: wrap; margin-bottom: 10px; }
.foot-name { color: var(--ink); font-weight: 600; }
.foot nav { display: flex; flex-wrap: wrap; gap: 4px 20px; }
.foot nav a { color: var(--soft); }
.foot p { margin: 0 0 6px; max-width: 86ch; }
.filing a { color: var(--soft); margin-left: 12px; }

@media (max-width: 900px) {
  .hero { grid-template-columns: 1fr; gap: 28px; }
  .steps { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 24px 24px; }
  .plain { grid-template-columns: 1fr; }
  .sheet { padding: 32px 26px; }
}
@media (max-width: 620px) {
  main, .top, .foot { padding-left: 16px; padding-right: 16px; }
  .kernel, .shots, .steps { grid-template-columns: 1fr; }
  .title-block { grid-template-columns: repeat(2, auto); }
  .title-block div:nth-child(2) { border-right: 0; }
  .title-block div:nth-child(-n+2) { border-bottom: 1px solid var(--line); }
  .log > li { grid-template-columns: 1fr; }
  .sheet { padding: 26px 20px; }
  section { margin-top: 48px; }
}