/* Set 3 ZH — sync lab: sticky compact bar, cool gray field, strip hero, timeline */
:root {
  --navy: #1e3a4c;
  --page: #eef3f7;
  --accent: #3b82c4;
  --accent-deep: #1d4f7a;
  --card: #ffffff;
  --ink: #163044;
  --muted: #4b6272;
  --line: #cfdbe4;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  font-family: "Helvetica Neue", "PingFang SC", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  background: var(--page);
  color: var(--ink);
  line-height: 1.68;
  font-size: 16px;
}

a { color: inherit; text-decoration: none; }
svg { display: block; }

.frame { width: min(1040px, calc(100% - 28px)); margin: 0 auto; }

.sticky-bar {
  position: sticky;
  top: 0;
  z-index: 20;
  background: var(--navy);
  color: #dbe7f0;
}

.sticky-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  min-height: 56px;
}

.mark {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 15px;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.tight-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 2px 12px;
  font-size: 12.5px;
}

.tight-nav a {
  padding: 7px 0;
  color: #b8c9d6;
}

.tight-nav a:hover,
.tight-nav a:focus {
  color: #ffffff;
  box-shadow: inset 0 -2px 0 var(--accent);
}

.hero-strip {
  background: linear-gradient(180deg, #d5e3ee 0%, var(--page) 100%);
  padding: 34px 0 18px;
  border-bottom: 1px solid var(--line);
}

.hero-strip h1 {
  font-size: clamp(24px, 2.8vw, 32px);
  line-height: 1.35;
  max-width: 22em;
  margin-bottom: 12px;
}

.hero-strip p {
  max-width: 52em;
  color: var(--muted);
  margin-bottom: 8px;
}

.section { padding: 36px 0; }
.section h2 {
  font-size: clamp(20px, 2.1vw, 26px);
  line-height: 1.4;
  margin-bottom: 10px;
}
.brief { color: var(--muted); max-width: 50em; margin-bottom: 20px; }

.split-devices {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 20px;
}

.prose p { color: var(--muted); margin-bottom: 12px; }

.dev-stack { display: grid; gap: 10px; }

.dev-card {
  display: grid;
  grid-template-columns: 52px 1fr;
  gap: 12px;
  background: var(--card);
  border: 1px solid var(--line);
  padding: 12px 14px;
  align-items: center;
}

.dev-card h3 { font-size: 15px; margin-bottom: 4px; }
.dev-card p { font-size: 13.5px; color: var(--muted); }

.timeline {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0;
  position: relative;
}

.timeline::before {
  content: "";
  position: absolute;
  left: 8%;
  right: 8%;
  top: 18px;
  height: 2px;
  background: #9ec3de;
}

.t-node {
  background: transparent;
  padding: 0 8px;
  position: relative;
}

.t-node i {
  display: block;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent);
  margin: 10px auto 14px;
  position: relative;
  z-index: 1;
}

.t-node h3 { font-size: 15px; text-align: center; margin-bottom: 8px; }
.t-node p {
  background: var(--card);
  border: 1px solid var(--line);
  padding: 12px;
  font-size: 13.5px;
  color: var(--muted);
}

.roles {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}

.role {
  background: var(--card);
  border-top: 4px solid var(--accent);
  padding: 18px 16px;
  min-height: 210px;
}

.role h3 { font-size: 16px; margin-bottom: 8px; }
.role p { font-size: 14px; color: var(--muted); }

.sheet {
  width: 100%;
  border-collapse: collapse;
  background: var(--card);
  font-size: 14px;
}

.sheet th,
.sheet td {
  border: 1px solid var(--line);
  padding: 12px 14px;
  text-align: left;
  vertical-align: top;
}

.sheet thead th { background: var(--navy); color: #e8f1f8; }
.sheet tbody th { width: 26%; background: #e4edf4; }

.check-list {
  display: grid;
  gap: 8px;
}

.check-list li {
  list-style: none;
  background: var(--card);
  border: 1px solid var(--line);
  padding: 12px 14px 12px 40px;
  position: relative;
  color: var(--muted);
}

.check-list li::before {
  content: "";
  width: 14px;
  height: 14px;
  border: 2px solid var(--accent);
  position: absolute;
  left: 14px;
  top: 16px;
}

.conflict {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.conflict article {
  background: var(--card);
  padding: 18px 16px;
  border: 1px dashed var(--accent);
}

.conflict h3 { font-size: 16px; margin-bottom: 8px; }
.conflict p { font-size: 14px; color: var(--muted); margin-bottom: 10px; }

.stable-steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  counter-reset: st;
}

.stable-steps article {
  background: var(--navy);
  color: #d7e6f1;
  padding: 16px 14px;
  min-height: 170px;
}

.stable-steps article::before {
  counter-increment: st;
  content: "0" counter(st);
  display: block;
  color: #7dd3fc;
  font-size: 12px;
  letter-spacing: 0.12em;
  margin-bottom: 8px;
}

.stable-steps h3 { font-size: 15px; margin-bottom: 8px; color: #fff; }
.stable-steps p { font-size: 13.5px; }

.faq details {
  background: var(--card);
  border: 1px solid var(--line);
  margin-bottom: 8px;
  padding: 0 14px;
}

.faq summary {
  cursor: pointer;
  font-weight: 700;
  font-size: 14.5px;
  padding: 12px 0;
}

.faq details p { color: var(--muted); padding: 0 0 14px; font-size: 14.5px; }

.base {
  background: var(--navy);
  color: #b9c9d6;
  padding: 28px 0 22px;
  font-size: 13.5px;
}

.base-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 12px;
}

.base h3 { color: #7dd3fc; font-size: 12px; margin-bottom: 6px; }
.base-copy { border-top: 1px solid #2c5166; padding-top: 12px; }

@media (max-width: 860px) {
  .split-devices,
  .timeline,
  .roles,
  .conflict,
  .stable-steps,
  .base-grid,
  .sticky-inner { grid-template-columns: 1fr; }
  .timeline::before { display: none; }
  .sticky-inner { padding: 8px 0; }
}