/* VR Research Hub — editorial dark theme */

:root {
  --bg: #0e1014;
  --bg-soft: #14161c;
  --bg-card: #171a21;
  --line: #262a33;
  --line-soft: #1f232b;
  --text: #e9e7e2;
  --text-dim: #9aa0ab;
  --text-faint: #6d737e;
  --accent: #7dd3c0;
  --accent-dim: #4a9c8c;
  --warm: #e8b98a;
  --radius: 14px;
  --max: 1120px;
  --read: 720px;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #faf9f6;
    --bg-soft: #f3f1ec;
    --bg-card: #ffffff;
    --line: #e2ded5;
    --line-soft: #ece9e2;
    --text: #1a1c20;
    --text-dim: #5c6169;
    --text-faint: #8d9299;
    --accent: #0f7d6c;
    --accent-dim: #0a5e51;
    --warm: #a8652b;
  }
}

* { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  font-size: 16px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a {
  color: inherit;
  text-decoration: none;
}

a:hover { color: var(--accent); }

/* ---------- header ---------- */

.site-head {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 18px max(24px, calc((100vw - var(--max)) / 2));
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(150%) blur(14px);
  border-bottom: 1px solid var(--line-soft);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 30px;
  height: 30px;
  border-radius: 8px;
  background: var(--text);
  color: var(--bg);
  font-size: 12px;
  font-weight: 800;
  letter-spacing: 0.02em;
}

.brand-text {
  font-size: 15px;
  color: var(--text-dim);
  font-weight: 600;
}

.site-nav {
  display: flex;
  gap: 4px;
  font-size: 14px;
}

.site-nav a {
  padding: 6px 13px;
  border-radius: 999px;
  color: var(--text-dim);
  transition: background 0.15s, color 0.15s;
}

.site-nav a:hover {
  background: var(--bg-soft);
  color: var(--text);
}

.site-nav a.is-active {
  background: var(--bg-soft);
  color: var(--text);
  font-weight: 600;
}

/* ---------- layout ---------- */

main {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 24px 96px;
}

.eyebrow {
  margin: 0 0 18px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.18em;
  color: var(--accent);
  text-transform: uppercase;
}

/* ---------- hero ---------- */

.hero {
  padding: 88px 0 56px;
  border-bottom: 1px solid var(--line-soft);
}

.hero h1 {
  margin: 0 0 24px;
  font-size: clamp(34px, 6vw, 58px);
  line-height: 1.18;
  letter-spacing: -0.025em;
  font-weight: 700;
}

.lede {
  max-width: 620px;
  margin: 0;
  font-size: 17px;
  line-height: 1.75;
  color: var(--text-dim);
}

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 1px;
  margin-top: 48px;
  background: var(--line-soft);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  overflow: hidden;
}

.stat {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 22px 20px;
  background: var(--bg);
}

.stat b {
  font-size: 30px;
  font-weight: 700;
  letter-spacing: -0.03em;
  font-variant-numeric: tabular-nums;
  line-height: 1.1;
}

.stat span {
  font-size: 12.5px;
  color: var(--text-faint);
  letter-spacing: 0.01em;
}

/* ---------- bands ---------- */

.band {
  padding: 56px 0;
  border-bottom: 1px solid var(--line-soft);
}

.band:last-child { border-bottom: none; }

.band-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 28px;
}

.band-head h2 {
  margin: 0;
  font-size: 21px;
  font-weight: 700;
  letter-spacing: -0.015em;
}

.more {
  font-size: 13.5px;
  color: var(--text-faint);
  transition: color 0.15s;
}

.more:hover { color: var(--accent); }

/* ---------- weekly feature ---------- */

.weekly-feature {
  display: block;
  padding: 32px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(150deg, var(--bg-card), var(--bg-soft));
  transition: border-color 0.2s, transform 0.2s;
}

.weekly-feature:hover {
  border-color: var(--accent-dim);
  transform: translateY(-2px);
  color: inherit;
}

.wf-date {
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.08em;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}

.weekly-feature h3 {
  margin: 12px 0 10px;
  font-size: clamp(20px, 3vw, 26px);
  line-height: 1.4;
  letter-spacing: -0.015em;
  font-weight: 600;
}

.weekly-feature p {
  margin: 0 0 18px;
  max-width: 640px;
  color: var(--text-dim);
  font-size: 15px;
}

.wf-cta {
  font-size: 13.5px;
  font-weight: 600;
  color: var(--accent);
}

/* ---------- paper cards ---------- */

.paper-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1px;
  background: var(--line-soft);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  overflow: hidden;
}

.paper-grid.wide {
  margin-top: 4px;
}

.paper {
  display: flex;
  flex-direction: column;
  padding: 24px;
  background: var(--bg);
  transition: background 0.15s;
  min-height: 172px;
}

.paper:hover { background: var(--bg-soft); }

.paper-date {
  font-size: 11.5px;
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.04em;
  color: var(--text-faint);
  margin-bottom: 10px;
}

.paper-pub {
  color: var(--warm);
  margin-left: 6px;
}

.paper-title {
  margin: 0 0 10px;
  font-size: 16px;
  line-height: 1.45;
  font-weight: 600;
  letter-spacing: -0.008em;
}

.paper-title a:hover { color: var(--accent); }

.paper-meta {
  margin: 0;
  font-size: 12.5px;
  line-height: 1.6;
  color: var(--text-faint);
}

.paper-meta .venue {
  color: var(--warm);
}

.paper-meta time {
  font-variant-numeric: tabular-nums;
}

.paper-abstract {
  margin: 12px 0 0;
  font-size: 13px;
  line-height: 1.68;
  color: var(--text-dim);
  display: -webkit-box;
  -webkit-line-clamp: 4;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.view-list .paper-abstract {
  -webkit-line-clamp: 2;
}

.paper-abstract.expanded {
  display: block;
  -webkit-line-clamp: unset;
  overflow: visible;
}

.abs-toggle {
  margin: 0 0 0 auto;
  padding: 0;
  border: 0;
  background: none;
  color: var(--accent);
  font-family: inherit;
  font-size: 12.5px;
  font-weight: 600;
  cursor: pointer;
  letter-spacing: 0.01em;
  white-space: nowrap;
}

.abs-toggle:hover {
  text-decoration: underline;
}

/* bottom row: 阅读 left, 展开 right */
.paper-foot {
  margin-top: auto;
  padding-top: 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.paper-foot .card-cta {
  margin-top: 0;
  padding-top: 0;
}

/* ---------- list view ---------- */

.paper-grid.view-list {
  display: block;
  border: 1px solid var(--line-soft);
}

.view-list .paper {
  min-height: 0;
  padding: 18px 24px;
  border-bottom: 1px solid var(--line-soft);
}

.view-list .paper:last-child {
  border-bottom: 0;
}

.view-list .paper-date {
  margin-bottom: 4px;
}

.view-list .paper-title {
  margin-bottom: 5px;
  font-size: 15.5px;
}

.view-list .card-cta {
  margin-top: 0;
  padding-top: 0;
  opacity: 1;
  transform: none;
}

.view-list .paper-foot {
  padding-top: 8px;
}

/* ---------- view toggle ---------- */

.viewtoggle {
  display: flex;
  gap: 1px;
  padding: 3px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--bg-soft);
}

.viewtoggle button {
  width: 34px;
  height: 32px;
  border: 0;
  border-radius: 7px;
  background: transparent;
  color: var(--text-faint);
  font-size: 15px;
  line-height: 1;
  cursor: pointer;
  font-family: inherit;
  transition: background 0.15s, color 0.15s;
}

.viewtoggle button:hover {
  color: var(--text);
}

.viewtoggle button.on {
  background: var(--line-soft);
  color: var(--accent);
}

.card-cta {
  margin-top: auto;
  padding-top: 16px;
  font-size: 12.5px;
  font-weight: 600;
  color: var(--accent);
  opacity: 0;
  transform: translateY(3px);
  transition: opacity 0.18s, transform 0.18s;
}

.paper:hover .card-cta {
  opacity: 1;
  transform: translateY(0);
}

@media (hover: none) {
  .card-cta { opacity: 1; transform: none; }
}

/* ---------- cta band ---------- */

.cta-band {
  text-align: center;
  padding: 72px 0;
}

.cta-band h2 {
  margin: 0 0 12px;
  font-size: clamp(22px, 3vw, 28px);
  letter-spacing: -0.02em;
}

.cta-band p {
  margin: 0 auto 26px;
  max-width: 460px;
  color: var(--text-dim);
  font-size: 15px;
}

.btn {
  display: inline-block;
  padding: 11px 26px;
  border-radius: 999px;
  background: var(--text);
  color: var(--bg);
  font-size: 14px;
  font-weight: 600;
  transition: opacity 0.15s;
}

.btn:hover { opacity: 0.82; color: var(--bg); }

/* ---------- page head ---------- */

.page-head {
  padding: 64px 0 36px;
  border-bottom: 1px solid var(--line-soft);
}

.page-head h1 {
  margin: 0 0 16px;
  font-size: clamp(30px, 5vw, 42px);
  letter-spacing: -0.025em;
  line-height: 1.2;
}

/* ---------- toolbar ---------- */

.toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  padding: 24px 0;
  position: sticky;
  top: 67px;
  background: var(--bg);
  z-index: 10;
}

.tb-main {
  display: flex;
  align-items: center;
  gap: 10px;
  flex: 1 1 320px;
  min-width: 0;
}

.tb-filters {
  display: flex;
  align-items: center;
  gap: 10px;
  flex: 0 1 auto;
}

.filter-toggle {
  display: none;
  align-items: center;
  gap: 5px;
  height: 40px;
  padding: 0 12px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--bg-soft);
  color: var(--text-dim);
  font-family: inherit;
  font-size: 13.5px;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
}

.filter-toggle.open {
  border-color: var(--accent-dim);
  color: var(--accent);
}

.filter-toggle .ft-caret {
  font-size: 10px;
  line-height: 1;
  transition: transform 0.18s;
}

.filter-toggle.open .ft-caret {
  transform: rotate(180deg);
}

.toolbar input,
.toolbar select {
  height: 40px;
  padding: 0 14px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--bg-soft);
  color: var(--text);
  font-size: 14px;
  font-family: inherit;
  outline: none;
  transition: border-color 0.15s;
}

.toolbar input:focus,
.toolbar select:focus {
  border-color: var(--accent-dim);
}

.toolbar input {
  flex: 1 1 auto;
  min-width: 0;
}

.toolbar select {
  flex: 0 1 auto;
  max-width: 200px;
}

.count {
  font-size: 12.5px;
  color: var(--text-faint);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
  flex: 0 0 auto;
}

/* ---------- issues ---------- */

.issues {
  display: flex;
  flex-direction: column;
  gap: 1px;
  margin-top: 36px;
  background: var(--line-soft);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius);
  overflow: hidden;
}

.issue {
  display: grid;
  grid-template-columns: 56px 1fr 24px;
  align-items: start;
  gap: 20px;
  padding: 26px 24px;
  background: var(--bg);
  transition: background 0.15s;
}

.issue:hover { background: var(--bg-soft); }

.issue-num {
  font-size: 13px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: var(--text-faint);
  padding-top: 3px;
}

.issue-body h3 {
  margin: 6px 0 8px;
  font-size: 17px;
  font-weight: 600;
  line-height: 1.45;
  letter-spacing: -0.008em;
}

.issue-date {
  font-size: 12px;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.03em;
}

.issue-body p {
  margin: 0;
  font-size: 14px;
  color: var(--text-dim);
  line-height: 1.65;
}

.issue-arrow {
  color: var(--text-faint);
  font-size: 16px;
  padding-top: 2px;
  transition: transform 0.15s, color 0.15s;
}

.issue:hover .issue-arrow {
  transform: translateX(3px);
  color: var(--accent);
}

/* ---------- issue page ---------- */

.issue-page {
  max-width: 780px;
  margin: 0 auto;
  padding-top: 40px;
}

.back {
  display: inline-block;
  font-size: 13px;
  color: var(--text-faint);
  margin-bottom: 32px;
}

.back:hover { color: var(--accent); }

.issue-head {
  padding-bottom: 32px;
  border-bottom: 1px solid var(--line-soft);
  margin-bottom: 40px;
}

.issue-kicker {
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.1em;
  color: var(--accent);
  margin-bottom: 16px;
  font-variant-numeric: tabular-nums;
}

.issue-head h1 {
  margin: 0 0 16px;
  font-size: clamp(26px, 4.5vw, 38px);
  line-height: 1.25;
  letter-spacing: -0.025em;
}

.issue-sub {
  margin: 0;
  font-size: 16px;
  line-height: 1.7;
  color: var(--text-dim);
}

.tagrow {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 22px;
}

.tag {
  padding: 4px 11px;
  border: 1px solid var(--line);
  border-radius: 999px;
  font-size: 12px;
  color: var(--text-faint);
}

/* ---------- prose ---------- */

.prose {
  font-size: 16.5px;
  line-height: 1.85;
  color: var(--text);
}

.prose.narrow { max-width: var(--read); }

.prose h1,
.prose h2 {
  margin: 48px 0 16px;
  font-size: 22px;
  letter-spacing: -0.015em;
  line-height: 1.4;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--line-soft);
}

.prose h1:first-child,
.prose h2:first-child { margin-top: 0; }

.prose h3 {
  margin: 34px 0 12px;
  font-size: 17.5px;
  letter-spacing: -0.01em;
  color: var(--text);
}

.prose h4 {
  margin: 26px 0 10px;
  font-size: 15.5px;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.prose p { margin: 0 0 20px; }

.prose a {
  color: var(--accent);
  border-bottom: 1px solid color-mix(in srgb, var(--accent) 35%, transparent);
  transition: border-color 0.15s;
  word-break: break-word;
}

.prose a:hover {
  border-bottom-color: var(--accent);
}

.prose ul,
.prose ol {
  margin: 0 0 22px;
  padding-left: 22px;
}

.prose li {
  margin-bottom: 9px;
  padding-left: 4px;
}

.prose li::marker { color: var(--text-faint); }

.prose strong {
  font-weight: 650;
  color: var(--text);
}

.prose blockquote {
  margin: 26px 0;
  padding: 4px 0 4px 20px;
  border-left: 2px solid var(--accent-dim);
  color: var(--text-dim);
}

.prose blockquote p { margin: 0 0 12px; }
.prose blockquote p:last-child { margin-bottom: 0; }

.prose code {
  padding: 2px 6px;
  border-radius: 5px;
  background: var(--bg-soft);
  border: 1px solid var(--line-soft);
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.88em;
}

.prose pre {
  margin: 24px 0;
  padding: 18px;
  border-radius: 10px;
  background: var(--bg-soft);
  border: 1px solid var(--line-soft);
  overflow-x: auto;
}

.prose pre code {
  padding: 0;
  border: none;
  background: none;
  font-size: 13px;
  line-height: 1.65;
}

.prose hr {
  margin: 40px 0;
  border: none;
  border-top: 1px solid var(--line-soft);
}

.prose table {
  width: 100%;
  margin: 24px 0;
  border-collapse: collapse;
  font-size: 14.5px;
}

.prose th,
.prose td {
  padding: 10px 14px;
  text-align: left;
  border-bottom: 1px solid var(--line-soft);
}

.prose th {
  font-weight: 600;
  color: var(--text-dim);
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

/* ---------- pager ---------- */

.pager {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 64px;
  padding-top: 28px;
  border-top: 1px solid var(--line-soft);
  font-size: 13.5px;
}

.pager a {
  color: var(--text-dim);
  font-variant-numeric: tabular-nums;
}

.pager a:hover { color: var(--accent); }

/* ---------- misc ---------- */

.empty {
  padding: 48px 24px;
  text-align: center;
  color: var(--text-faint);
  font-size: 14.5px;
  border: 1px dashed var(--line);
  border-radius: var(--radius);
}

.site-foot {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  justify-content: center;
  padding: 40px 24px 56px;
  border-top: 1px solid var(--line-soft);
  font-size: 12.5px;
  color: var(--text-faint);
}

.site-foot .dot { color: var(--line); }

/* ---------- responsive ---------- */

@media (max-width: 720px) {
  .site-head {
    padding: 14px 18px;
    gap: 12px;
  }

  .brand-text { display: none; }

  .site-nav a {
    padding: 6px 10px;
    font-size: 13.5px;
  }

  main { padding: 0 18px 64px; }

  .hero { padding: 56px 0 40px; }

  .hero h1 { font-size: 32px; }

  .lede { font-size: 15.5px; }

  .stats { grid-template-columns: repeat(2, 1fr); }

  .stat { padding: 18px 16px; }

  .stat b { font-size: 24px; }

  .band { padding: 40px 0; }

  .weekly-feature { padding: 24px; }

  .page-head {
    padding: 28px 0 20px;
  }

  .page-head h1 {
    margin-bottom: 8px;
  }

  .page-head .lede {
    font-size: 14px;
    line-height: 1.6;
  }

  .toolbar {
    top: 58px;
    padding: 10px 0;
    gap: 8px;
    flex-wrap: wrap;
  }

  .tb-main {
    flex: 1 1 100%;
    min-width: 0;
    gap: 6px;
  }

  .toolbar input {
    flex: 1 1 auto;
    min-width: 0;
    height: 38px;
    font-size: 15px;
  }

  .filter-toggle {
    display: inline-flex;
    height: 38px;
    padding: 0 10px;
    font-size: 13px;
    gap: 3px;
  }

  .viewtoggle button {
    width: 30px;
    height: 30px;
    font-size: 14px;
  }

  .tb-filters {
    display: none;
    flex: 1 1 100%;
    width: 100%;
    flex-wrap: nowrap;
    gap: 8px;
    padding-top: 8px;
  }

  .tb-filters.open {
    display: flex;
  }

  .toolbar select {
    flex: 1 1 0;
    min-width: 0;
    max-width: none;
    height: 38px;
  }

  .paper-grid { grid-template-columns: 1fr; }

  .issue {
    grid-template-columns: 36px 1fr;
    gap: 14px;
    padding: 20px 18px;
  }

  .issue-arrow { display: none; }

  .issue-page { padding-top: 28px; }

  .prose { font-size: 16px; }

  .prose table { font-size: 13.5px; }

  .prose th, .prose td { padding: 8px 10px; }
}

/* very narrow phones: give the search box room */
@media (max-width: 359px) {
  .count { display: none; }
}