:root {
  --bg: #fbfaf7;
  --card: #ffffff;
  --ink: #1d1a16;
  --ink-soft: #4c4842;
  --ink-mute: #8a857c;
  --line: #e8e3d8;
  --line-soft: #f1ece0;
  --accent: #c14b5a;
  --accent-soft: #fce8ec;
  --accent-bg: #fff7f8;
  --muted-bg: #f5f0e3;
}
* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Helvetica Neue", "Segoe UI", Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.75;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  text-size-adjust: 100%;
  -webkit-text-size-adjust: 100%;
}
a { color: var(--accent); text-decoration: none; }

.page {
  max-width: 720px;
  margin: 0 auto;
  padding: 20px 20px 80px;
}

/* =========== Masthead (index) =========== */
.masthead { padding: 8px 0 32px; border-bottom: 1px solid var(--line); margin-bottom: 32px; }
.masthead .eyebrow {
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--ink-mute);
  text-transform: uppercase;
  margin-bottom: 14px;
}
.masthead h1 {
  font-size: 26px;
  line-height: 1.4;
  margin: 0 0 16px;
  font-weight: 700;
  letter-spacing: -0.01em;
}
.masthead .subtitle {
  font-size: 15px;
  color: var(--ink-soft);
  margin: 0;
}
.masthead .meta {
  display: flex;
  gap: 20px;
  margin-top: 18px;
  font-size: 12px;
  color: var(--ink-mute);
  flex-wrap: wrap;
}

.conclusions { margin-bottom: 40px; }
.conclusions-label, .chapters-label {
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--ink-mute);
  margin-bottom: 16px;
}
.chapters-label { margin: 40px 0 16px; }

.conclusion-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: 8px;
  padding: 18px 20px;
  margin-bottom: 12px;
}
.conclusion-card .tag {
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 600;
  margin-bottom: 8px;
}
.conclusion-card .headline {
  font-size: 15.5px;
  font-weight: 700;
  margin-bottom: 8px;
  line-height: 1.55;
}
.conclusion-card .body {
  font-size: 14.5px;
  color: var(--ink-soft);
  line-height: 1.7;
}

.chapter-link {
  display: flex;
  gap: 16px;
  align-items: flex-start;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 18px 20px;
  margin-bottom: 10px;
  color: var(--ink);
  transition: border-color 0.15s, transform 0.1s;
  min-height: 64px;
}
.chapter-link:active { transform: scale(0.99); }
.chapter-link:hover { border-color: var(--accent); }
.chapter-link .num {
  font-size: 28px;
  font-weight: 700;
  color: var(--ink-mute);
  line-height: 1;
  font-variant-numeric: tabular-nums;
  min-width: 32px;
  margin-top: -2px;
}
.chapter-link .copy h3 {
  margin: 0 0 4px;
  font-size: 16px;
  font-weight: 700;
  line-height: 1.4;
}
.chapter-link .copy p {
  margin: 0;
  font-size: 13.5px;
  color: var(--ink-mute);
  line-height: 1.55;
}
.chapter-link .arrow {
  margin-left: auto;
  color: var(--ink-mute);
  font-size: 18px;
  align-self: center;
  flex-shrink: 0;
}
.chapter-link.disabled {
  opacity: 0.55;
  pointer-events: none;
}

footer.site {
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
  font-size: 12px;
  color: var(--ink-mute);
}

/* =========== Chapter page =========== */
.topnav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 0 24px;
  font-size: 13px;
}
.topnav a {
  color: var(--ink-mute);
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 2px;
  min-height: 44px;
}
.topnav a:active { color: var(--accent); }
.topnav .progress { color: var(--ink-mute); }

.ch-head {
  display: flex;
  align-items: baseline;
  gap: 16px;
  padding-bottom: 20px;
  border-bottom: 2px solid var(--ink);
  margin-bottom: 24px;
}
.ch-head .num {
  font-size: 56px;
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.02em;
}
.ch-head .title h1 {
  margin: 0 0 4px;
  font-size: 22px;
  font-weight: 700;
  line-height: 1.35;
  letter-spacing: -0.01em;
}
.ch-head .title .kicker {
  font-size: 12.5px;
  color: var(--ink-mute);
  line-height: 1.5;
}

.ch-intro {
  font-size: 15.5px;
  color: var(--ink-soft);
  margin: 0 0 16px;
}

.note {
  background: var(--muted-bg);
  border-radius: 8px;
  padding: 12px 16px;
  margin: 16px 0 24px;
  font-size: 14px;
  color: var(--ink-soft);
  line-height: 1.7;
}
.note strong { color: var(--ink); }

.expand-all {
  background: none;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 7px 14px;
  font-size: 12.5px;
  color: var(--ink-soft);
  cursor: pointer;
  margin-bottom: 12px;
  font-family: inherit;
  min-height: 36px;
}
.expand-all:active { background: var(--muted-bg); }

/* Details / collapsible */
details.sub {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  margin-bottom: 10px;
  overflow: hidden;
}
details.sub[open] { border-color: #d6d0bf; }
details.sub > summary {
  list-style: none;
  padding: 16px 18px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 12px;
  min-height: 56px;
  user-select: none;
}
details.sub > summary::-webkit-details-marker { display: none; }
details.sub > summary::marker { content: ""; }
details.sub > summary .sub-num {
  font-size: 12.5px;
  color: var(--ink-mute);
  font-variant-numeric: tabular-nums;
  font-weight: 600;
  letter-spacing: 0.04em;
  flex-shrink: 0;
  min-width: 32px;
}
details.sub > summary .sub-title {
  font-size: 15.5px;
  font-weight: 700;
  line-height: 1.45;
  flex: 1;
}
details.sub > summary .sub-title .hint {
  display: block;
  font-size: 12.5px;
  font-weight: 400;
  color: var(--ink-mute);
  margin-top: 3px;
  line-height: 1.5;
}
details.sub > summary .chev {
  flex-shrink: 0;
  width: 20px;
  height: 20px;
  color: var(--ink-mute);
  transition: transform 0.2s ease;
  margin-left: 4px;
}
details.sub[open] > summary .chev { transform: rotate(90deg); }
details.sub > .sub-body {
  padding: 4px 18px 22px;
  border-top: 1px solid var(--line-soft);
  padding-top: 16px;
}
details.sub > .sub-body > *:first-child { margin-top: 0; }
details.sub > .sub-body > *:last-child { margin-bottom: 0; }
details.sub > .sub-body p {
  margin: 0 0 12px;
  font-size: 15px;
  color: var(--ink-soft);
  line-height: 1.75;
}
details.sub > .sub-body p strong { color: var(--ink); }
details.sub > .sub-body ul, details.sub > .sub-body ol {
  padding-left: 22px;
  margin: 0 0 12px;
  font-size: 15px;
  color: var(--ink-soft);
}
details.sub > .sub-body ul li, details.sub > .sub-body ol li { margin-bottom: 6px; }
details.sub > .sub-body h4 {
  margin: 20px 0 10px;
  font-size: 14.5px;
  font-weight: 700;
  color: var(--ink);
}
details.sub > .sub-body h4:first-child { margin-top: 0; }

/* Nested subtopic (e.g., 3.0.1 within 3.0) */
.subtopic {
  margin: 18px 0;
  padding: 14px 0 2px;
  border-top: 1px solid var(--line-soft);
}
.subtopic:first-child { padding-top: 0; border-top: none; }
.subtopic > h5 {
  margin: 0 0 10px;
  font-size: 14px;
  font-weight: 700;
  color: var(--ink);
}
.subtopic > h5 .num {
  display: inline-block;
  font-size: 11.5px;
  color: var(--ink-mute);
  font-weight: 600;
  margin-right: 6px;
  font-variant-numeric: tabular-nums;
}

/* Tables */
.table-wrap {
  margin: 14px -18px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
table.data {
  width: 100%;
  min-width: 480px;
  border-collapse: collapse;
  font-size: 14px;
}
table.data th, table.data td {
  padding: 10px 14px;
  text-align: left;
  border-bottom: 1px solid var(--line-soft);
  vertical-align: top;
}
table.data th {
  background: #faf6ec;
  font-weight: 600;
  color: var(--ink);
  font-size: 12.5px;
  letter-spacing: 0.02em;
  white-space: nowrap;
}
table.data tbody tr:last-child td { border-bottom: none; }
table.data td.num { font-variant-numeric: tabular-nums; color: var(--ink-soft); }
table.data td strong { color: var(--ink); }
table.data small { color: var(--ink-mute); font-size: 12px; }
table.data .pct-bar {
  display: inline-block;
  height: 5px;
  background: var(--accent);
  border-radius: 3px;
  vertical-align: middle;
  margin-right: 6px;
  opacity: 0.7;
}

/* Quote — subtle by default */
.quote {
  margin: 12px 0;
  padding: 2px 14px;
  border-left: 2px solid var(--line);
  font-size: 14px;
  color: var(--ink-soft);
  line-height: 1.7;
}
.quote .text {
  margin: 0 0 6px;
}
.quote .cite {
  font-size: 12px;
  color: var(--ink-mute);
  line-height: 1.5;
}
.quote .cite a { color: var(--ink-mute); border-bottom: 1px dotted var(--ink-mute); }
.quote .cite a:active { color: var(--accent); border-bottom-color: var(--accent); }
.quote .cite .meta-sep { margin: 0 6px; opacity: 0.5; }
.quote .cite .likes { font-variant-numeric: tabular-nums; }
.quote.pin {
  border-left-color: var(--accent);
  padding-top: 4px;
  padding-bottom: 4px;
}
.quote.pin .pin-tag {
  display: inline-block;
  font-size: 10.5px;
  letter-spacing: 0.1em;
  padding: 1px 6px;
  border-radius: 4px;
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
  margin-bottom: 6px;
  text-transform: uppercase;
}
.quote .persona {
  font-size: 11.5px;
  color: var(--ink-mute);
}

/* Insight */
.insight {
  background: var(--accent-bg);
  border: 1px solid var(--accent-soft);
  border-radius: 8px;
  padding: 16px 18px;
  margin: 16px 0;
}
.insight .label {
  font-size: 11px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 700;
  margin-bottom: 8px;
}
.insight h4 {
  font-size: 15px;
  margin: 0 0 8px;
  font-weight: 700;
}
.insight p, .insight ul, .insight ol {
  margin: 0;
  font-size: 14px;
  color: var(--ink-soft);
  line-height: 1.7;
}
.insight ul, .insight ol { padding-left: 18px; }
.insight li { margin-bottom: 4px; }
.insight li:last-child { margin-bottom: 0; }
.insight p + p { margin-top: 8px; }

/* Key findings bordered list */
.findings {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 16px 20px;
  margin: 16px 0;
}
.findings h4 {
  font-size: 11.5px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-mute);
  margin: 0 0 10px;
  font-weight: 600;
}
.findings ol, .findings ul {
  margin: 0;
  padding-left: 20px;
  font-size: 14.5px;
}
.findings li { margin-bottom: 8px; }
.findings li:last-child { margin-bottom: 0; }

/* Brand chip */
.brand {
  display: inline-block;
  padding: 1px 8px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
  background: var(--muted-bg);
  color: var(--ink-soft);
  white-space: nowrap;
}
.brand.oura { background: #e4ecf0; color: #3b5a6b; }
.brand.ringconn { background: #ece7d6; color: #6b5f3b; }
.brand.dreame { background: #eedde7; color: #7a4a6a; }
.brand.whoop { background: #dde8dd; color: #3f5a3f; }
.brand.apple { background: #e9e5de; color: #4a4740; }
.brand.samsung { background: #e1e5ea; color: #3b4858; }
.brand.hqb { background: #eae0d4; color: #6e5943; }

/* Price ladder */
.price-ladder { margin: 16px 0; }
.ladder-row {
  display: grid;
  grid-template-columns: 100px 1fr;
  gap: 12px;
  align-items: center;
  padding: 10px 0;
  border-bottom: 1px dashed var(--line-soft);
  font-size: 13.5px;
}
.ladder-row:last-child { border-bottom: none; }
.ladder-row .range {
  font-variant-numeric: tabular-nums;
  font-weight: 700;
  font-size: 13.5px;
  color: var(--ink);
}
.ladder-row .bar-wrap {
  position: relative;
  height: 8px;
  background: var(--line-soft);
  border-radius: 4px;
  overflow: hidden;
  margin-bottom: 4px;
}
.ladder-row .bar {
  position: absolute;
  top: 0;
  height: 100%;
  border-radius: 4px;
}
.ladder-row .tag {
  font-size: 12.5px;
  color: var(--ink-soft);
  line-height: 1.5;
}

/* Hack ranking bars (chapter 4) */
.hack-bar-list { margin: 14px 0; }
.hack-bar {
  display: grid;
  grid-template-columns: 1fr;
  gap: 4px;
  padding: 10px 0;
  border-bottom: 1px dashed var(--line-soft);
  font-size: 13.5px;
}
.hack-bar:last-child { border-bottom: none; }
.hack-bar .row1 {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 8px;
}
.hack-bar .name { font-weight: 700; color: var(--ink); }
.hack-bar .pct { font-variant-numeric: tabular-nums; font-weight: 600; color: var(--accent); font-size: 13px; }
.hack-bar .bar-wrap { height: 10px; background: var(--line-soft); border-radius: 5px; overflow: hidden; }
.hack-bar .bar { height: 100%; background: var(--accent); border-radius: 5px; }
.hack-bar .brand-line { font-size: 12px; color: var(--ink-mute); }

/* Pager */
.pager {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
}
.pager a {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 14px 16px;
  min-height: 60px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  color: var(--ink);
}
.pager a .dir {
  font-size: 11px;
  color: var(--ink-mute);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 4px;
}
.pager a .label { font-size: 14px; font-weight: 600; line-height: 1.4; }
.pager a.disabled { opacity: 0.4; pointer-events: none; }
.pager a.next { text-align: right; }

.back-to-index {
  text-align: center;
  margin-top: 24px;
}
.back-to-index a {
  color: var(--ink-mute);
  font-size: 13px;
  padding: 10px;
  display: inline-block;
}

/* Responsive */
@media (min-width: 640px) {
  .page { padding: 32px 32px 100px; }
  .masthead h1 { font-size: 32px; }
  .masthead .subtitle { font-size: 16px; }
  .ch-head .num { font-size: 64px; }
  .ch-head .title h1 { font-size: 26px; }
  .table-wrap { margin: 14px 0; }
}