/* Set 3 — zh: left rail + warm reading column */
:root {
  --rail: #fff7ed;
  --paper: #fffbeb;
  --ink: #431407;
  --soft: #9a3412;
  --line: #fdba74;
  --brand: #c2410c;
  --deep: #7c2d12;
  --card: #ffffff;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html { overflow-x: hidden; }
body {
  min-height: 100%;
  font-family: Georgia, "Songti SC", "SimSun", "PingFang SC", "Microsoft YaHei", serif;
  background: var(--paper);
  color: var(--ink);
  line-height: 1.85;
  font-size: 17px;
}
a { color: var(--brand); }
img, .brand svg {
  display: block;
  max-width: 100%;
}
p svg, li svg, dd svg {
  width: 1.1em;
  height: 1.1em;
  display: inline-block;
  vertical-align: -0.2em;
  margin: 0 2px;
}
.frame {
  display: grid;
  grid-template-columns: 240px minmax(0, 1fr);
  grid-template-rows: 1fr auto;
  min-height: 100vh;
}
.rail {
  grid-column: 1;
  grid-row: 1;
  align-self: start;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow: auto;
  background: var(--rail);
  border-right: 1px solid var(--line);
  padding: 28px 18px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
  font-weight: 800;
  font-size: 20px;
  color: var(--brand);
  margin-bottom: 28px;
  line-height: 1.2;
}
.brand svg { width: 28px; height: 28px; flex-shrink: 0; }
.rail nav ul { list-style: none; }
.rail nav a {
  display: block;
  padding: 10px 12px;
  margin-bottom: 6px;
  text-decoration: none;
  color: var(--deep);
  border-left: 3px solid transparent;
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
  font-weight: 600;
}
.rail nav a.is-on {
  background: #ffedd5;
  border-left-color: var(--brand);
  color: var(--brand);
}
.story {
  grid-column: 2;
  grid-row: 1;
  min-width: 0;
  padding: 36px 40px 64px;
  max-width: 880px;
}
.story h1 {
  font-size: clamp(26px, 3vw, 32px);
  line-height: 1.35;
  margin: 8px 0 18px;
  word-break: break-word;
}
.eyebrow {
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
  font-size: 12px;
  letter-spacing: 0.12em;
  color: var(--brand);
  font-weight: 700;
}
.lead { font-size: 18px; margin-bottom: 20px; }
.story p { margin-bottom: 12px; }
.dl-stack {
  background: var(--card);
  border: 1px solid var(--line);
  padding: 16px 18px;
  margin: 8px 0 28px;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}
.btn {
  display: inline-block;
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
  background: var(--brand);
  color: #fff;
  padding: 11px 18px;
  text-decoration: none;
  font-weight: 700;
  line-height: 1.3;
}
.btn:hover { filter: brightness(1.06); }
.btn.alt {
  background: #fff;
  color: var(--brand);
  border: 1px solid var(--brand);
}
.chapter { margin: 32px 0; }
.chapter h2 {
  font-size: 22px;
  color: var(--deep);
  margin-bottom: 12px;
  line-height: 1.4;
}
.note {
  border-top: 1px solid var(--line);
  padding-top: 10px;
  margin-top: 10px;
  color: var(--soft);
}
.story ol { padding-left: 22px; margin: 10px 0 16px; }
.story li { margin-bottom: 8px; }
.story table {
  width: 100%;
  border-collapse: collapse;
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
  font-size: 15px;
  table-layout: fixed;
  word-break: break-word;
  margin: 12px 0 16px;
  background: #fff;
}
th, td { border: 1px solid #fed7aa; padding: 8px 10px; text-align: left; }
th { background: #ffedd5; }
.faq dt {
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
  font-weight: 700;
  margin-top: 16px;
}
.faq dd { color: var(--soft); margin: 6px 0 0; }
.colophon {
  grid-column: 1 / -1;
  grid-row: 2;
  background: #7c2d12;
  color: #ffedd5;
  padding: 24px 40px 32px;
  font-family: "Segoe UI", "Microsoft YaHei", sans-serif;
  font-size: 14px;
  line-height: 1.7;
}
.colophon p { margin-bottom: 8px; }
@media (max-width: 900px) {
  .frame {
    grid-template-columns: minmax(0, 1fr);
    grid-template-rows: auto 1fr auto;
  }
  .rail {
    grid-column: 1;
    grid-row: 1;
    position: relative;
    height: auto;
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }
  .story {
    grid-column: 1;
    grid-row: 2;
    padding: 24px 18px 48px;
  }
  .colophon {
    grid-column: 1;
    grid-row: 3;
    padding: 20px 18px 28px;
  }
}