/* ==========================================================================
   壹趣体育看台 · 共享样式 /assets/site.css
   夜空深蓝底 + 经幡五色标签 + 等宽数据 + 玻璃层与实色层并置
   ========================================================================== */

/* ---------- 1. Reset ---------- */
*,
*::before,
*::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 1rem);
}

body { margin: 0; }

h1, h2, h3, h4, p, figure, blockquote, dl, dd { margin: 0; }

ul, ol { margin: 0; padding: 0; list-style: none; }

img, picture, svg, video { display: block; max-width: 100%; }

button, input, select, textarea { font: inherit; color: inherit; }

a { color: inherit; }

/* ---------- 2. Tokens ---------- */
:root {
  --ink-900: #0A1120;
  --ink-800: #111B2E;
  --ink-700: #1B2740;
  --ink-600: #22304D;
  --glass: rgba(255, 255, 255, 0.06);
  --glass-strong: rgba(255, 255, 255, 0.10);
  --line: #2A3A57;
  --line-strong: #3A4F76;
  --text-1: #EEF2F8;
  --text-2: #A9B6CB;
  --stone: #6E7A8B;
  --flag-blue: #3A8FE0;
  --flag-white: #F3F0E4;
  --flag-red: #E0524A;
  --flag-yellow: #EFB63C;
  --flag-green: #49A97A;

  --font-heading: 'Barlow Condensed', 'Saira Condensed', 'Source Han Sans SC', 'PingFang SC', sans-serif;
  --font-body: 'Source Han Sans SC', 'Noto Sans SC', 'PingFang SC', sans-serif;
  --font-data: 'JetBrains Mono', 'IBM Plex Mono', 'Roboto Mono', monospace;

  --wrap: 1260px;
  --gutter: 1rem;
  --gap: clamp(0.85rem, 1.6vw, 1.4rem);
  --header-h: 5.25rem;
  --radius: 3px;
  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

@media (min-width: 768px) {
  :root { --gutter: 2rem; }
}

@media (min-width: 901px) {
  :root { --header-h: 6.5rem; }
}

/* ---------- 3. Base & typography ---------- */
body {
  position: relative;
  min-height: 100vh;
  background-color: var(--ink-900);
  background-image: radial-gradient(125% 70% at 50% -12%, rgba(58, 143, 224, 0.16), transparent 68%),
                    radial-gradient(90% 55% at 8% 108%, rgba(73, 169, 122, 0.08), transparent 70%);
  background-repeat: no-repeat;
  color: var(--text-1);
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.75;
  font-weight: 400;
  letter-spacing: 0.005em;
}

/* 高原星空：固定星点层，不参与滚动，不是视差 */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    radial-gradient(1px 1px at 13% 21%, rgba(243, 240, 228, 0.55), transparent 100%),
    radial-gradient(1px 1px at 77% 12%, rgba(243, 240, 228, 0.42), transparent 100%),
    radial-gradient(1px 1px at 33% 63%, rgba(243, 240, 228, 0.30), transparent 100%),
    radial-gradient(1px 1px at 64% 79%, rgba(243, 240, 228, 0.34), transparent 100%),
    radial-gradient(1px 1px at 89% 54%, rgba(243, 240, 228, 0.26), transparent 100%),
    radial-gradient(1px 1px at 7% 83%, rgba(243, 240, 228, 0.30), transparent 100%),
    radial-gradient(1px 1px at 46% 34%, rgba(58, 143, 224, 0.45), transparent 100%),
    radial-gradient(1px 1px at 22% 47%, rgba(243, 240, 228, 0.22), transparent 100%);
}

h1 {
  font-family: var(--font-heading);
  font-size: clamp(2.4rem, 5.2vw, 4.6rem);
  line-height: 1.02;
  letter-spacing: -0.01em;
  font-weight: 600;
  color: var(--text-1);
}

h2 {
  font-family: var(--font-heading);
  font-size: clamp(1.6rem, 2.6vw, 2.4rem);
  line-height: 1.12;
  letter-spacing: -0.005em;
  font-weight: 600;
  color: var(--text-1);
}

h3 {
  font-family: var(--font-heading);
  font-size: 1.25rem;
  line-height: 1.3;
  letter-spacing: 0;
  font-weight: 600;
  color: var(--text-1);
}

h4 {
  font-size: 1rem;
  line-height: 1.5;
  font-weight: 600;
  color: var(--text-1);
}

a { text-decoration-color: transparent; }
a:hover { text-decoration-color: currentColor; }

.yt-num {
  font-family: var(--font-data);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0;
}

.yt-kicker {
  font-family: var(--font-data);
  font-size: 0.75rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--flag-blue);
}

.yt-lede {
  font-size: clamp(1rem, 1.35vw, 1.125rem);
  line-height: 1.8;
  color: var(--text-2);
  max-width: 36em;
}

.yt-vertical {
  writing-mode: vertical-rl;
  text-orientation: mixed;
  font-family: var(--font-data);
  font-size: 0.75rem;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--stone);
}

.yt-prose {
  max-width: 38em;
  font-size: 1.0625rem;
  line-height: 1.75;
  color: var(--text-1);
}

.yt-prose p + p { margin-top: 1em; }
.yt-prose h2 { margin-top: 2.2em; margin-bottom: 0.6em; }
.yt-prose h3 { margin-top: 1.8em; margin-bottom: 0.5em; }
.yt-prose ul, .yt-prose ol { margin: 1em 0; padding-left: 1.3em; color: var(--text-2); }
.yt-prose ul { list-style: disc; }
.yt-prose ol { list-style: decimal; }
.yt-prose a { color: var(--flag-blue); }
.yt-prose strong { color: var(--text-1); }

.yt-rule {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  border-top: 1px solid var(--line);
  padding-top: 0.75rem;
  font-family: var(--font-data);
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  color: var(--stone);
}

/* ---------- 4. Layout ---------- */
.yt-container {
  width: min(100% - (var(--gutter) * 2), var(--wrap));
  margin-inline: auto;
}

#main-content {
  position: relative;
  z-index: 1;
  padding-top: var(--header-h);
}

.yt-hero {
  position: relative;
  z-index: 1;
  margin-top: calc(var(--header-h) * -1);
  padding-top: calc(var(--header-h) + clamp(2rem, 6vw, 4.5rem));
  padding-bottom: clamp(2rem, 5vw, 3.5rem);
}

.yt-hero__grid {
  display: grid;
  grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
  gap: clamp(1.5rem, 4vw, 3rem);
  align-items: start;
}

.yt-hero__rail {
  display: flex;
  gap: 1.25rem;
  align-items: flex-start;
}

.yt-hero__lede { margin-top: clamp(1rem, 2vw, 1.5rem); }

.yt-hero__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1rem;
  margin-top: clamp(1rem, 2vw, 1.5rem);
  font-family: var(--font-data);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  color: var(--stone);
}

.yt-section { padding-block: clamp(2rem, 5vw, 3.5rem); }
.yt-section--ruled { border-top: 1px solid var(--line); }

.yt-section__head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.5rem 1.25rem;
  margin-bottom: clamp(1.25rem, 3vw, 2rem);
}

.yt-grid { display: grid; gap: var(--gap); }
.yt-grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.yt-grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.yt-grid--4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.yt-grid--7-4 { grid-template-columns: minmax(0, 7fr) minmax(0, 4fr); }
.yt-grid--8-4 { grid-template-columns: minmax(0, 8fr) minmax(0, 4fr); }
.yt-grid--index { grid-template-columns: minmax(0, 3fr) minmax(0, 9fr); }

.yt-stack { display: flex; flex-direction: column; gap: var(--gap); }
.yt-cluster { display: flex; flex-wrap: wrap; align-items: center; gap: 0.5rem 0.75rem; }

/* ---------- 5. Header ---------- */
.yt-skip {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 200;
  display: inline-block;
  padding: 0.7rem 1.1rem;
  background: var(--flag-white);
  color: var(--ink-900);
  font-family: var(--font-heading);
  font-size: 1rem;
  letter-spacing: 0.04em;
  text-decoration: none;
  border-radius: 0 0 var(--radius) 0;
}

.yt-skip:focus { left: 0; }

.yt-header {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 60;
  color: var(--text-1);
}

/* 顶部状态条 */
.yt-statusbar {
  background: var(--ink-800);
  border-bottom: 1px solid var(--line);
  color: var(--text-2);
  font-family: var(--font-data);
  font-size: 0.72rem;
  letter-spacing: 0.04em;
  transition: background 0.18s var(--ease), border-color 0.18s var(--ease), color 0.18s var(--ease);
}

.yt-statusbar__inner {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  min-height: 1.75rem;
  padding-block: 0.15rem;
  overflow-x: auto;
  scrollbar-width: none;
}

.yt-statusbar__inner::-webkit-scrollbar { display: none; }

.yt-statusbar__item {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  white-space: nowrap;
}

.yt-statusbar__dot {
  width: 0.5rem;
  height: 0.5rem;
  flex: 0 0 auto;
  border-radius: 50%;
  background: var(--flag-green);
  box-shadow: 0 0 0 3px rgba(73, 169, 122, 0.18);
}

.yt-statusbar__strong { color: var(--flag-green); font-weight: 400; }
.yt-statusbar__num { color: var(--text-1); font-weight: 400; }

.yt-statusbar__divider {
  width: 1px;
  height: 0.85rem;
  flex: 0 0 auto;
  background: var(--line);
}

.yt-statusbar__link {
  margin-left: auto;
  padding-left: 0.9rem;
  border-left: 1px solid var(--line);
  color: var(--flag-blue);
  text-decoration: none;
  white-space: nowrap;
}

.yt-statusbar__link:hover { text-decoration: underline; }

.yt-statusbar[data-state="warn"] {
  background: #241F10;
  border-bottom-color: rgba(239, 182, 60, 0.45);
  color: #EBD9AE;
}

.yt-statusbar[data-state="warn"] .yt-statusbar__dot {
  background: var(--flag-yellow);
  box-shadow: 0 0 0 3px rgba(239, 182, 60, 0.22);
}

.yt-statusbar[data-state="warn"] .yt-statusbar__strong,
.yt-statusbar[data-state="warn"] .yt-statusbar__num,
.yt-statusbar[data-state="warn"] .yt-statusbar__link { color: var(--flag-yellow); }

/* 导航条 */
.yt-header__bar {
  background: transparent;
  border-bottom: 1px solid transparent;
  transition: background 0.18s var(--ease), border-color 0.18s var(--ease);
}

.yt-header[data-scrolled="true"] .yt-header__bar {
  background: var(--ink-800);
  border-bottom-color: var(--line);
}

.yt-header__inner {
  display: flex;
  align-items: center;
  gap: clamp(0.75rem, 2vw, 1.75rem);
  min-height: 3.5rem;
}

@media (min-width: 901px) {
  .yt-header__inner { min-height: 4.5rem; }
}

.yt-brand {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  flex: 0 0 auto;
  text-decoration: none;
}

.yt-brand__mark {
  display: grid;
  place-items: center;
  width: 2.1rem;
  height: 2.1rem;
  flex: 0 0 auto;
  border-radius: 2px;
  background: var(--flag-white);
  color: var(--ink-900);
  font-family: var(--font-heading);
  font-size: 1.2rem;
  font-weight: 600;
  line-height: 1;
}

.yt-brand__text { display: block; }

.yt-brand__name {
  display: block;
  font-family: var(--font-heading);
  font-size: 1.2rem;
  font-weight: 600;
  line-height: 1.1;
  letter-spacing: -0.01em;
}

.yt-brand__tagline {
  display: block;
  font-size: 0.75rem;
  line-height: 1.3;
  color: var(--text-2);
  letter-spacing: 0.02em;
}

.yt-nav {
  display: flex;
  flex: 1 1 auto;
  justify-content: flex-end;
}

.yt-nav__list {
  display: flex;
  align-items: center;
  gap: clamp(0.4rem, 1.5vw, 1.4rem);
}

.yt-nav__item { display: block; }

.yt-nav__link {
  display: inline-block;
  padding: 0.5rem 0.15rem 0.45rem;
  font-family: var(--font-heading);
  font-size: 1.0625rem;
  letter-spacing: 0.02em;
  color: var(--text-2);
  text-decoration: none;
  border-bottom: 2px solid transparent;
  transition: color 0.15s var(--ease), border-color 0.15s var(--ease);
}

.yt-nav__link:hover { color: var(--text-1); }

.yt-nav__link[aria-current="page"] {
  color: var(--text-1);
  border-bottom-color: var(--flag-blue);
}

.yt-header__actions {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex: 0 0 auto;
}

.yt-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -1px;
  height: 2px;
  background: var(--flag-blue);
  opacity: 0.9;
  transform-origin: left center;
  transform: scaleX(var(--p, 0));
}

/* 移动导航按钮 */
.yt-navtoggle {
  display: none;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 0.7rem;
  background: var(--glass);
  border: 1px solid var(--line);
  border-radius: 2px;
  color: var(--text-1);
  font-family: var(--font-heading);
  font-size: 0.9375rem;
  letter-spacing: 0.06em;
  cursor: pointer;
  transition: background 0.15s var(--ease), border-color 0.15s var(--ease);
}

.yt-navtoggle:hover { background: var(--glass-strong); border-color: var(--line-strong); }

.yt-navtoggle__bars {
  display: inline-flex;
  flex-direction: column;
  justify-content: center;
  gap: 3px;
  width: 16px;
}

.yt-navtoggle__bar {
  display: block;
  height: 2px;
  background: currentColor;
}

.yt-navtoggle__label { display: inline-block; }

/* ---------- 6. Footer ---------- */
.yt-footer {
  position: relative;
  z-index: 1;
  margin-top: clamp(3rem, 8vw, 6rem);
  background: var(--ink-800);
  border-top: 1px solid var(--line);
  color: var(--text-2);
}

.yt-flagline {
  display: flex;
  height: 3px;
  width: 100%;
}

.yt-flagline i { flex: 1 1 20%; display: block; }
.yt-flagline i:nth-child(1) { background: var(--flag-blue); }
.yt-flagline i:nth-child(2) { background: var(--flag-white); }
.yt-flagline i:nth-child(3) { background: var(--flag-red); }
.yt-flagline i:nth-child(4) { background: var(--flag-green); }
.yt-flagline i:nth-child(5) { background: var(--flag-yellow); }

.yt-footer__inner { padding-block: clamp(2.25rem, 5vw, 3.5rem) 1.5rem; }

.yt-footer__grid {
  display: grid;
  grid-template-columns: minmax(0, 1.5fr) repeat(3, minmax(0, 1fr));
  gap: clamp(1.5rem, 4vw, 3rem);
}

.yt-footer__brand {
  font-family: var(--font-heading);
  font-size: 1.35rem;
  font-weight: 600;
  line-height: 1.2;
  color: var(--text-1);
}

.yt-footer__tagline {
  margin-top: 0.4rem;
  font-size: 0.875rem;
  color: var(--text-2);
}

.yt-footer__meta {
  display: grid;
  gap: 0.5rem;
  margin-top: 1.1rem;
  font-size: 0.875rem;
  line-height: 1.7;
}

.yt-footer__meta-key {
  display: inline-block;
  min-width: 4.6rem;
  font-family: var(--font-data);
  font-size: 0.75rem;
  letter-spacing: 0.1em;
  color: var(--stone);
}

.yt-footer__title {
  font-family: var(--font-data);
  font-size: 0.75rem;
  font-weight: 400;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--stone);
  margin-bottom: 0.9rem;
}

.yt-footer__list { display: grid; gap: 0.55rem; }

.yt-footer__link {
  font-size: 0.9375rem;
  color: var(--text-2);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 0.15s var(--ease), border-color 0.15s var(--ease);
}

.yt-footer__link:hover {
  color: var(--text-1);
  border-bottom-color: var(--flag-blue);
}

.yt-footer__base {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.5rem 1.5rem;
  margin-top: clamp(2rem, 4vw, 3rem);
  padding-top: 1.1rem;
  border-top: 1px solid var(--line);
  font-size: 0.8125rem;
  color: var(--stone);
}

.yt-footer__legal,
.yt-footer__copy { font-family: var(--font-data); letter-spacing: 0.04em; }

.yt-footer__note { flex: 1 1 22rem; line-height: 1.7; }

/* ---------- 7. Buttons ---------- */
.yt-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.55rem 1rem;
  border: 1px solid var(--line-strong);
  border-radius: 2px;
  background: transparent;
  color: var(--text-1);
  font-family: var(--font-heading);
  font-size: 1rem;
  letter-spacing: 0.04em;
  text-decoration: none;
  cursor: pointer;
  transition: background 0.15s var(--ease), border-color 0.15s var(--ease), color 0.15s var(--ease), transform 0.15s var(--ease);
}

.yt-btn:hover { background: var(--glass); border-color: var(--flag-blue); }

.yt-btn--ghost { background: var(--glass); }

.yt-btn--solid {
  background: var(--flag-white);
  border-color: var(--flag-white);
  color: var(--ink-900);
}

.yt-btn--solid:hover {
  background: #FFFFFF;
  border-color: #FFFFFF;
  color: var(--ink-900);
}

/* ---------- 8. Tags ---------- */
.yt-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.3rem 0.5rem;
  border: 1px solid var(--line);
  border-radius: 2px;
  background: var(--glass);
  color: var(--text-2);
  font-family: var(--font-data);
  font-size: 0.72rem;
  line-height: 1;
  letter-spacing: 0.05em;
  white-space: nowrap;
}

.yt-tag--blue { color: #BFE0FF; border-color: rgba(58, 143, 224, 0.5); background: rgba(58, 143, 224, 0.14); }
.yt-tag--white { color: var(--flag-white); border-color: rgba(243, 240, 228, 0.45); background: rgba(243, 240, 228, 0.10); }
.yt-tag--red { color: #FFC9C5; border-color: rgba(224, 82, 74, 0.55); background: rgba(224, 82, 74, 0.16); }
.yt-tag--yellow { color: #F7DFA6; border-color: rgba(239, 182, 60, 0.55); background: rgba(239, 182, 60, 0.15); }
.yt-tag--green { color: #B7E7CE; border-color: rgba(73, 169, 122, 0.5); background: rgba(73, 169, 122, 0.15); }

/* ---------- 9. Cards & notes ---------- */
.yt-card {
  padding: clamp(0.9rem, 1.6vw, 1.25rem);
  background: var(--ink-700);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.yt-card--glass {
  background: var(--glass);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.yt-card--white {
  background: var(--flag-white);
  border-color: var(--flag-white);
  color: var(--ink-900);
}

.yt-card--white h3,
.yt-card--white .yt-num { color: var(--ink-900); }

.yt-card--hover {
  transition: transform 0.15s var(--ease), background 0.15s var(--ease), border-color 0.15s var(--ease);
}

.yt-card--hover:hover {
  transform: translateY(-2px);
  background: var(--ink-600);
  border-color: var(--line-strong);
}

.yt-note {
  padding-left: 0.85rem;
  border-left: 2px solid var(--line);
  font-size: 0.875rem;
  line-height: 1.7;
  color: var(--text-2);
}

.yt-note--blue { border-left-color: var(--flag-blue); }
.yt-note--yellow { border-left-color: var(--flag-yellow); }

/* ---------- 10. Table ---------- */
.yt-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9375rem;
}

.yt-table th,
.yt-table td {
  padding: 0.6rem 0.7rem;
  border-bottom: 1px solid var(--line);
  text-align: left;
  vertical-align: baseline;
}

.yt-table th {
  font-family: var(--font-data);
  font-size: 0.72rem;
  font-weight: 400;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--stone);
}

.yt-table td.yt-num,
.yt-table th.yt-num { text-align: right; }

.yt-table tbody tr { transition: background 0.15s var(--ease); }
.yt-table tbody tr:hover { background: var(--glass); }

/* ---------- 11. Figure ---------- */
.yt-figure { margin: 0; }

.yt-figure__media {
  position: relative;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(180deg, var(--ink-700), var(--ink-800));
  aspect-ratio: 16 / 9;
  min-height: 8rem;
}

.yt-figure__media > img,
.yt-figure__media > picture > img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.yt-figure--panorama .yt-figure__media { aspect-ratio: 21 / 9; }
.yt-figure--board .yt-figure__media { aspect-ratio: 3 / 2; }
.yt-figure--tall .yt-figure__media { aspect-ratio: 4 / 5; }

.yt-figure__cap {
  margin-top: 0.6rem;
  font-size: 0.8125rem;
  line-height: 1.6;
  color: var(--stone);
}

/* ---------- 12. Sticky index ---------- */
.yt-index {
  padding: 1rem;
  background: var(--glass);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.yt-index__title {
  margin-bottom: 0.75rem;
  font-family: var(--font-data);
  font-size: 0.72rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--stone);
}

.yt-index__list { display: grid; gap: 0.1rem; }

.yt-index__link {
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
  padding: 0.5rem 0.6rem;
  border-left: 2px solid transparent;
  color: var(--text-2);
  font-size: 0.9375rem;
  text-decoration: none;
  transition: color 0.12s var(--ease), background 0.12s var(--ease), border-color 0.12s var(--ease);
}

.yt-index__link:hover {
  color: var(--text-1);
  background: var(--glass-strong);
}

.yt-index__link.is-active {
  color: var(--text-1);
  border-left-color: var(--flag-blue);
  background: var(--glass-strong);
}

.yt-index--sticky {
  position: sticky;
  top: calc(var(--header-h) + 1rem);
}

/* ---------- 13. Tabs ---------- */
.yt-tabs { display: block; }

.yt-tabs__list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  margin-bottom: var(--gap);
  border-bottom: 1px solid var(--line);
}

.yt-tab {
  appearance: none;
  margin-bottom: -1px;
  padding: 0.5rem 0.85rem;
  background: transparent;
  border: 1px solid transparent;
  border-bottom: 2px solid transparent;
  border-radius: 2px 2px 0 0;
  color: var(--text-2);
  font-family: var(--font-heading);
  font-size: 1rem;
  letter-spacing: 0.03em;
  cursor: pointer;
  transition: color 0.15s var(--ease), background 0.15s var(--ease), border-color 0.15s var(--ease);
}

.yt-tab:hover { color: var(--text-1); background: var(--glass); }

.yt-tab[aria-selected="true"] {
  color: var(--text-1);
  background: var(--glass);
  border-bottom-color: var(--flag-blue);
}

.yt-tabpanel { animation: yt-fade 0.15s var(--ease); }
.yt-tabpanel[hidden] { display: none; }

@keyframes yt-fade {
  from { opacity: 0; }
  to { opacity: 1; }
}

/* ---------- 14. Breadcrumb ---------- */
.yt-breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-data);
  font-size: 0.72rem;
  letter-spacing: 0.06em;
  color: var(--stone);
}

.yt-breadcrumb__link { color: var(--text-2); text-decoration: none; }
.yt-breadcrumb__link:hover { color: var(--flag-blue); }
.yt-breadcrumb__sep { color: var(--line-strong); }
.yt-breadcrumb__current { color: var(--text-1); }

/* ---------- 15. Utilities ---------- */
.yt-visually-hidden {
  position: absolute !important;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

/* ---------- 16. Focus & motion ---------- */
:focus-visible {
  outline: 2px solid var(--flag-blue);
  outline-offset: 2px;
}

.yt-skip:focus-visible { outline-offset: 0; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }

  .yt-card--hover:hover { transform: none; }
}

/* ---------- 17. Responsive ---------- */
@media (max-width: 1180px) {
  .yt-brand__tagline { display: none; }
}

@media (max-width: 1100px) {
  .yt-grid--4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 1024px) {
  .yt-hero__grid { grid-template-columns: 1fr; }
  .yt-grid--7-4,
  .yt-grid--8-4,
  .yt-grid--index { grid-template-columns: 1fr; }
  .yt-index--sticky { position: static; }
  .yt-footer__grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

/* 移动端导航 */
@media (max-width: 900px) {
  .yt-navtoggle { display: inline-flex; }

  .yt-nav {
    position: fixed;
    inset: var(--header-h) 0 auto 0;
    display: none;
    max-height: calc(100vh - var(--header-h));
    overflow-y: auto;
    padding: 0.5rem var(--gutter) 1.25rem;
    background: var(--ink-800);
    border-bottom: 1px solid var(--line);
    box-shadow: 0 18px 32px rgba(0, 0, 0, 0.45);
  }

  .yt-nav[data-open="true"] { display: block; }

  .yt-nav__list { flex-direction: column; align-items: stretch; gap: 0; }

  .yt-nav__item { width: 100%; }

  .yt-nav__link {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.85rem 0.5rem;
    border-bottom: 1px solid var(--line);
    font-size: 1.125rem;
  }

  .yt-nav__link[aria-current="page"] {
    border-bottom-color: var(--line);
    border-left: 2px solid var(--flag-blue);
    padding-left: 0.75rem;
    background: var(--glass);
  }
}

@media (max-width: 720px) {
  .yt-grid--2,
  .yt-grid--3 { grid-template-columns: 1fr; }
}

@media (max-width: 600px) {
  .yt-footer__grid { grid-template-columns: 1fr; }
  .yt-header__cta { display: none; }
  .yt-brand__mark { width: 1.9rem; height: 1.9rem; font-size: 1.05rem; }
  .yt-brand__name { font-size: 1.1rem; }
  .yt-statusbar { font-size: 0.68rem; }
}

@media (max-width: 420px) {
  .yt-navtoggle__label { display: none; }
}