/* ============================================
   BSPORTS 全站共享样式 — /assets/site.css
   ============================================ */

/* ---------- 1. Reset ---------- */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
  scroll-behavior: smooth;
}

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

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

button {
  border: none;
  background: none;
  cursor: pointer;
}

ul,
ol {
  list-style: none;
}

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

/* ---------- 2. CSS 变量 ---------- */
:root {
  --clr-bg: #0D1B2A;
  --clr-bg-secondary: #1B263B;
  --clr-accent: #00FF9D;
  --clr-accent-dark: #00C48C;
  --clr-gold: #FFD700;
  --clr-light: #F2F3F5;
  --clr-white: #FFFFFF;
  --clr-dark: #1A1A1A;

  --font-heading: system-ui, -apple-system, "Helvetica Neue", Arial, sans-serif;
  --font-body: system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
  --heading-weight: 800;
  --body-weight: 400;
  --line-height: 1.7;

  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 1rem;
  --space-4: 1.5rem;
  --space-5: 2rem;
  --space-6: 3rem;
  --space-7: 4rem;
  --space-8: 6rem;

  --container-max: 1200px;
  --container-pad: 1.5rem;
  --header-h: 4.5rem;
  --header-h-mobile: 3.5rem;

  --transition-fast: 0.15s ease;
  --transition-base: 0.25s ease;
}

/* ---------- 3. 基础排版与全局 ---------- */
body {
  font-family: var(--font-body);
  font-weight: var(--body-weight);
  font-size: 1rem;
  line-height: var(--line-height);
  color: var(--clr-white);
  background-color: var(--clr-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-heading);
  font-weight: var(--heading-weight);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  text-wrap: balance;
}

p {
  text-wrap: pretty;
}

::selection {
  background-color: var(--clr-accent);
  color: var(--clr-dark);
}

:focus-visible {
  outline: 2px solid var(--clr-gold);
  outline-offset: 2px;
}

::-webkit-scrollbar {
  width: 0.625rem;
  height: 0.625rem;
  background-color: var(--clr-bg);
}

::-webkit-scrollbar-thumb {
  background-color: var(--clr-bg-secondary);
  border-radius: 2px;
  border: 2px solid var(--clr-bg);
}

::-webkit-scrollbar-thumb:hover {
  background-color: var(--clr-accent-dark);
}

/* ---------- 4. 布局工具 ---------- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--container-pad);
}

.content-area {
  padding-top: var(--space-6);
  padding-bottom: var(--space-8);
}

#main-content {
  flex: 1 0 auto;
  width: 100%;
  scroll-margin-top: var(--header-h-mobile);
}

@media (min-width: 821px) {
  #main-content {
    scroll-margin-top: calc(var(--header-h) + 0.5rem);
  }
}

.surface-light {
  background-color: var(--clr-light);
  color: var(--clr-dark);
  border-radius: 4px;
}

.surface-light h1,
.surface-light h2,
.surface-light h3,
.surface-light h4,
.surface-light h5,
.surface-light h6 {
  color: var(--clr-dark);
}

/* ---------- 5. 页头 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background-color: var(--clr-bg-secondary);
  border-bottom: 1px solid rgba(0, 255, 157, 0.25);
}

.scroll-progress {
  position: absolute;
  top: 0;
  left: 0;
  height: 3px;
  width: 0;
  background-color: var(--clr-accent);
  box-shadow: 0 0 8px rgba(0, 255, 157, 0.5);
  z-index: 10;
}

.site-header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  min-height: var(--header-h);
  position: relative;
}

/* ---------- 6. 品牌 ---------- */
.brand-link {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  flex-shrink: 0;
}

.brand-mark {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  background-color: var(--clr-accent);
  border-radius: 3px;
  transform: skewX(-8deg);
  box-shadow: 0 0 12px rgba(0, 255, 157, 0.35);
  flex-shrink: 0;
}

.brand-mark::before {
  content: "";
  display: block;
  width: 1.1rem;
  height: 1.1rem;
  background-color: var(--clr-bg);
  transform: rotate(45deg);
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1;
}

.brand-name {
  font-family: var(--font-heading);
  font-size: 1.375rem;
  font-weight: var(--heading-weight);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--clr-white);
}

.brand-tagline {
  font-family: var(--font-heading);
  font-size: 0.6875rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--clr-gold);
  margin-top: 0.25rem;
}

/* ---------- 7. 主导航 ---------- */
.site-nav-list {
  display: flex;
  align-items: center;
  gap: 0.125rem;
}

.site-nav-item {
  position: relative;
}

.site-nav-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.625rem 0.75rem;
  font-family: var(--font-heading);
  font-size: 0.8125rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: rgba(255, 255, 255, 0.85);
  border: 1px solid transparent;
  border-radius: 3px;
  transition: background-color var(--transition-fast), color var(--transition-fast), border-color var(--transition-fast);
}

.site-nav-index {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 1.375rem;
  padding: 0.125rem 0.25rem;
  font-size: 0.625rem;
  font-weight: 600;
  line-height: 1.2;
  text-align: center;
  color: var(--clr-gold);
  background: rgba(255, 215, 0, 0.08);
  border: 1px solid rgba(255, 215, 0, 0.3);
  border-radius: 3px;
  transition: background-color var(--transition-fast), color var(--transition-fast), border-color var(--transition-fast);
}

.site-nav-text {
  display: inline-block;
}

.site-nav-link:hover {
  background-color: var(--clr-accent);
  border-color: var(--clr-accent);
  color: var(--clr-dark);
}

.site-nav-link:hover .site-nav-index {
  background-color: var(--clr-bg);
  border-color: var(--clr-bg);
  color: var(--clr-gold);
}

.site-nav-link[aria-current="page"] {
  background-color: rgba(0, 255, 157, 0.08);
  border-color: rgba(0, 255, 157, 0.35);
  color: var(--clr-accent);
}

.site-nav-link[aria-current="page"]::after {
  content: "";
  position: absolute;
  bottom: -1px;
  left: 0.75rem;
  right: 0.75rem;
  height: 2px;
  background-color: var(--clr-gold);
}

.site-nav-link[aria-current="page"]:hover {
  background-color: var(--clr-accent);
  border-color: var(--clr-accent);
  color: var(--clr-dark);
}

/* ---------- 8. 移动端导航按钮 ---------- */
.nav-toggle {
  display: none;
}

.nav-toggle-line {
  display: block;
  width: 1.25rem;
  height: 2px;
  background-color: var(--clr-accent);
  border-radius: 2px;
  transition: transform var(--transition-fast), opacity var(--transition-fast), background-color var(--transition-fast);
}

/* ---------- 9. 页脚 ---------- */
.site-footer {
  position: relative;
  background-color: var(--clr-bg);
  border-top: 1px solid rgba(0, 255, 157, 0.25);
}

.site-footer::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--clr-accent) 0%, var(--clr-accent) 68%, var(--clr-gold) 68%, var(--clr-gold) 100%);
  z-index: 1;
}

.site-footer::after {
  content: "";
  position: absolute;
  top: 4px;
  bottom: 0;
  right: 0;
  width: 28%;
  background: linear-gradient(135deg, rgba(0, 255, 157, 0.03) 0%, rgba(255, 215, 0, 0.02) 100%);
  pointer-events: none;
}

.site-footer-main {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1.2fr;
  gap: var(--space-6);
  padding-top: var(--space-7);
  padding-bottom: var(--space-6);
}

.site-footer-brand {
  position: relative;
}

.site-footer-brand .brand-link {
  margin-bottom: var(--space-4);
}

.site-footer-statement {
  font-size: 0.8125rem;
  color: rgba(255, 255, 255, 0.55);
  border-left: 2px solid var(--clr-gold);
  padding-left: var(--space-3);
  max-width: 34rem;
}

.site-footer-col h2 {
  margin-bottom: var(--space-3);
}

.site-footer-heading {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--clr-gold);
}

.site-footer-heading-mark {
  display: block;
  width: 1.5rem;
  height: 3px;
  background-color: var(--clr-accent);
  flex-shrink: 0;
}

.site-footer-list li {
  margin-bottom: 0.5rem;
}

.site-footer-list a {
  display: inline-flex;
  align-items: center;
  gap: 0.375rem;
  color: rgba(255, 255, 255, 0.7);
  font-size: 0.875rem;
  font-weight: 500;
  transition: color var(--transition-fast);
}

.site-footer-list a::before {
  content: "→";
  color: var(--clr-accent);
  font-size: 0.75rem;
  opacity: 0;
  transform: translateX(-4px);
  transition: opacity var(--transition-fast), transform var(--transition-fast);
}

.site-footer-list a:hover {
  color: var(--clr-accent);
}

.site-footer-list a:hover::before {
  opacity: 1;
  transform: translateX(0);
}

.site-footer-contact li {
  color: rgba(255, 255, 255, 0.7);
  font-size: 0.875rem;
  line-height: 1.6;
  padding-left: 0.75rem;
  border-left: 1px solid rgba(0, 255, 157, 0.3);
}

.site-footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  background-color: rgba(0, 0, 0, 0.25);
}

.site-footer-bottom-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-4);
  padding-top: var(--space-4);
  padding-bottom: var(--space-4);
}

.site-footer-copyright,
.site-footer-icp {
  margin: 0;
  font-size: 0.8125rem;
  color: rgba(255, 255, 255, 0.5);
  letter-spacing: 0.02em;
}

/* ---------- 10. 返回顶部 ---------- */
.back-to-top {
  position: fixed;
  right: 1.5rem;
  bottom: 1.5rem;
  z-index: 900;
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.125rem;
  width: 3.25rem;
  height: 3.25rem;
  background-color: var(--clr-accent);
  color: var(--clr-dark);
  border-radius: 4px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.35);
  opacity: 0;
  visibility: hidden;
  transform: translateY(0.75rem);
  transition: opacity var(--transition-base), transform var(--transition-base), visibility var(--transition-base), background-color var(--transition-fast);
  cursor: pointer;
}

.back-to-top:hover {
  background-color: var(--clr-gold);
}

.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top-icon {
  font-size: 1.25rem;
  line-height: 1;
  display: block;
}

.back-to-top-text {
  font-size: 0.5625rem;
  font-family: var(--font-heading);
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

/* ---------- 11. 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  font-family: var(--font-heading);
  font-size: 0.875rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  border: 1px solid transparent;
  border-radius: 3px;
  cursor: pointer;
  transition: background-color var(--transition-fast), color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.btn:focus-visible {
  outline: 2px solid var(--clr-gold);
  outline-offset: 2px;
}

.btn-primary {
  background-color: var(--clr-accent);
  color: var(--clr-dark);
  border-color: var(--clr-accent);
}

.btn-primary:hover {
  background-color: transparent;
  color: var(--clr-accent);
  box-shadow: inset 0 0 0 1px var(--clr-accent);
}

.btn-outline {
  background-color: transparent;
  color: var(--clr-accent);
  border-color: var(--clr-accent);
}

.btn-outline:hover {
  background-color: var(--clr-accent);
  color: var(--clr-dark);
}

.btn-ghost {
  background-color: transparent;
  color: var(--clr-white);
  border-color: rgba(255, 255, 255, 0.35);
}

.btn-ghost:hover {
  border-color: var(--clr-gold);
  color: var(--clr-gold);
}

/* ---------- 12. 面包屑 ---------- */
.breadcrumbs {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.5rem;
  font-size: 0.8125rem;
  margin-bottom: var(--space-5);
  color: rgba(255, 255, 255, 0.6);
}

.breadcrumbs li {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.breadcrumbs li + li::before {
  content: "/";
  color: var(--clr-gold);
  font-size: 0.75rem;
}

.breadcrumbs a {
  color: rgba(255, 255, 255, 0.7);
  transition: color var(--transition-fast);
}

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

.breadcrumbs [aria-current="page"] {
  color: var(--clr-accent);
}

/* ---------- 13. 页面标题区 ---------- */
.page-header {
  padding-top: var(--space-7);
  padding-bottom: var(--space-6);
  position: relative;
}

.page-header::after {
  content: "";
  display: block;
  width: 4rem;
  height: 3px;
  background-color: var(--clr-accent);
  margin-top: var(--space-4);
}

.page-title {
  font-size: clamp(2.25rem, 5vw, 3.5rem);
  line-height: 1.1;
  color: var(--clr-white);
}

.page-description {
  font-size: 1.0625rem;
  color: rgba(255, 255, 255, 0.75);
  max-width: 46rem;
  margin-top: var(--space-3);
}

/* ---------- 14. 区块标签与分割 ---------- */
.section-label {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  font-family: var(--font-heading);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--clr-gold);
  margin-bottom: var(--space-3);
}

.section-label::before {
  content: "";
  width: 2rem;
  height: 2px;
  background-color: var(--clr-accent);
}

.section-title {
  font-size: clamp(1.75rem, 3.5vw, 2.5rem);
  line-height: 1.15;
  color: var(--clr-white);
  margin-bottom: var(--space-4);
}

.divider {
  border: none;
  height: 1px;
  background: linear-gradient(90deg, var(--clr-accent) 0%, rgba(0, 255, 157, 0.15) 40%, transparent 100%);
  margin: var(--space-6) 0;
}

/* ---------- 15. 栅格 ---------- */
.grid {
  display: grid;
  gap: var(--space-5);
}

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

.grid-3 {
  grid-template-columns: repeat(3, 1fr);
}

.grid-4 {
  grid-template-columns: repeat(4, 1fr);
}

/* ---------- 16. 卡片 ---------- */
.card {
  background-color: var(--clr-bg-secondary);
  border: 1px solid rgba(0, 255, 157, 0.15);
  border-radius: 4px;
  padding: var(--space-5);
  position: relative;
  overflow: hidden;
  transition: transform var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 3px;
  height: 0;
  background-color: var(--clr-accent);
  transition: height var(--transition-base);
}

.card:hover {
  transform: translateY(-4px);
  border-color: rgba(0, 255, 157, 0.4);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.3), 0 0 0 1px rgba(0, 255, 157, 0.1);
}

.card:hover::before {
  height: 100%;
}

.card-heading {
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--clr-white);
  margin-bottom: var(--space-2);
}

.card-body {
  font-size: 0.9375rem;
  color: rgba(255, 255, 255, 0.75);
}

.card-link {
  display: inline-flex;
  align-items: center;
  gap: 0.375rem;
  margin-top: var(--space-3);
  font-family: var(--font-heading);
  font-size: 0.8125rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--clr-accent);
  transition: color var(--transition-fast);
}

.card-link::after {
  content: "→";
  transition: transform var(--transition-fast);
}

.card-link:hover {
  color: var(--clr-gold);
}

.card-link:hover::after {
  transform: translateX(4px);
}

/* ---------- 17. 图片容器 ---------- */
.img-frame {
  position: relative;
  display: block;
  width: 100%;
  aspect-ratio: 4 / 3;
  background-color: var(--clr-bg-secondary);
  border: 1px solid rgba(0, 255, 157, 0.2);
  overflow: hidden;
}

.img-frame::before {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: 2.25rem;
  height: 2.25rem;
  background: linear-gradient(135deg, transparent 50%, var(--clr-gold) 50%);
  z-index: 2;
  pointer-events: none;
}

.img-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--transition-base);
}

.img-frame:hover img {
  transform: scale(1.02);
}

.img-frame.-wide {
  aspect-ratio: 16 / 9;
}

.img-frame.-tall {
  aspect-ratio: 3 / 4;
}

.img-frame.-skew {
  transform: skewX(-4deg);
}

.img-frame.-skew > * {
  transform: skewX(4deg);
  display: block;
  width: 100%;
  height: 100%;
}

/* ---------- 18. 时间轴 ---------- */
.timeline {
  position: relative;
  padding-left: 2rem;
}

.timeline::before {
  content: "";
  position: absolute;
  top: 0.25rem;
  bottom: 0.25rem;
  left: 0.5rem;
  width: 2px;
  background: linear-gradient(180deg, var(--clr-accent) 0%, var(--clr-gold) 100%);
}

.timeline-item {
  position: relative;
  padding-bottom: var(--space-5);
}

.timeline-item::before {
  content: "";
  position: absolute;
  top: 0.25rem;
  left: -2rem;
  width: 0.625rem;
  height: 0.625rem;
  border-radius: 50%;
  background-color: var(--clr-bg);
  border: 3px solid var(--clr-accent);
}

.timeline-item.is-current::before {
  background-color: var(--clr-gold);
  border-color: var(--clr-gold);
  box-shadow: 0 0 0 4px rgba(255, 215, 0, 0.2);
}

/* ---------- 19. 折叠面板 ---------- */
.accordion-item {
  border: 1px solid rgba(0, 255, 157, 0.15);
  border-radius: 4px;
  margin-bottom: var(--space-3);
  background-color: var(--clr-bg-secondary);
  overflow: hidden;
  transition: border-color var(--transition-fast);
}

.accordion-item:hover {
  border-color: rgba(0, 255, 157, 0.4);
}

.accordion-trigger {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  padding: var(--space-4);
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.9375rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--clr-white);
  background-color: transparent;
  text-align: left;
  cursor: pointer;
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

.accordion-trigger::after {
  content: "+";
  flex-shrink: 0;
  font-size: 1.25rem;
  font-weight: 400;
  color: var(--clr-accent);
  transition: transform var(--transition-fast), color var(--transition-fast);
}

.accordion-trigger:hover {
  color: var(--clr-accent);
}

.accordion-trigger[aria-expanded="true"] {
  color: var(--clr-accent);
  background-color: rgba(0, 255, 157, 0.05);
}

.accordion-trigger[aria-expanded="true"]::after {
  content: "−";
  color: var(--clr-gold);
}

.accordion-panel {
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  visibility: hidden;
  transition: max-height var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
}

.accordion-panel[data-open] {
  max-height: 25rem;
  opacity: 1;
  visibility: visible;
}

.accordion-panel-inner {
  padding: 0 var(--space-4) var(--space-4);
}

.accordion-panel-inner *:last-child {
  margin-bottom: 0;
}

/* ---------- 20. 响应式 ---------- */
@media (min-width: 821px) and (max-width: 1100px) {
  .brand-tagline {
    display: none;
  }

  .site-nav-link {
    padding: 0.5rem 0.5rem;
    font-size: 0.75rem;
  }

  .site-footer-main {
    grid-template-columns: 1.5fr 1fr 1fr;
    gap: var(--space-5);
  }

  .site-footer-col:last-child {
    grid-column: 2 / -1;
  }
}

@media (max-width: 820px) {
  .site-header-inner {
    min-height: var(--header-h-mobile);
    gap: var(--space-2);
  }

  .nav-toggle {
    display: inline-flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 4px;
    width: 2.75rem;
    height: 2.75rem;
    border: 1px solid rgba(0, 255, 157, 0.35);
    border-radius: 4px;
    background-color: rgba(0, 255, 157, 0.05);
    cursor: pointer;
    position: relative;
    z-index: 200;
    transition: border-color var(--transition-fast), background-color var(--transition-fast);
  }

  .nav-toggle:hover {
    border-color: var(--clr-accent);
    background-color: rgba(0, 255, 157, 0.1);
  }

  .nav-toggle[aria-expanded="true"] {
    border-color: var(--clr-gold);
  }

  .nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(1) {
    transform: translateY(6px) rotate(45deg);
    background-color: var(--clr-gold);
  }

  .nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(2) {
    opacity: 0;
  }

  .nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(3) {
    transform: translateY(-6px) rotate(-45deg);
    background-color: var(--clr-gold);
  }

  .site-nav {
    position: fixed;
    top: var(--header-h-mobile);
    left: 0;
    right: 0;
    z-index: 150;
    background-color: var(--clr-bg-secondary);
    border-bottom: 3px solid var(--clr-accent);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
    max-height: calc(100vh - var(--header-h-mobile));
    overflow-y: auto;
    padding: var(--space-3) var(--space-2);
    transform: translateY(-0.5rem);
    opacity: 0;
    visibility: hidden;
    transition: transform var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
  }

  .site-nav[data-open] {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .site-nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
  }

  .site-nav-link {
    justify-content: space-between;
    padding: 1rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.06);
    border-radius: 0;
    border-left: 3px solid transparent;
  }

  .site-nav-link[aria-current="page"] {
    background-color: rgba(0, 255, 157, 0.1);
    border-left-color: var(--clr-gold);
    color: var(--clr-accent);
  }

  .site-nav-link[aria-current="page"]::after {
    display: none;
  }

  .site-nav-link:hover {
    background-color: var(--clr-accent);
    border-left-color: var(--clr-accent);
    color: var(--clr-dark);
  }

  .site-footer-main {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-5) var(--space-4);
    padding-top: var(--space-6);
  }

  .site-footer-brand {
    grid-column: 1 / -1;
  }
}

@media (max-width: 640px) {
  .brand-tagline {
    display: none;
  }

  .brand-name {
    font-size: 1.125rem;
  }

  .brand-mark {
    width: 2.25rem;
    height: 2.25rem;
  }

  .brand-mark::before {
    width: 0.9375rem;
    height: 0.9375rem;
  }

  .site-footer-main {
    grid-template-columns: 1fr;
    gap: var(--space-5);
  }

  .site-footer-brand {
    grid-column: auto;
  }

  .page-header {
    padding-top: var(--space-6);
    padding-bottom: var(--space-5);
  }

  .content-area {
    padding-top: var(--space-4);
    padding-bottom: var(--space-6);
  }

  .grid-2,
  .grid-3,
  .grid-4 {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  :root {
    --container-pad: 1rem;
  }

  .back-to-top {
    width: 2.75rem;
    height: 2.75rem;
    right: 1rem;
    bottom: 1rem;
  }

  .back-to-top-text {
    font-size: 0.5rem;
  }
}

/* ---------- 21. 无障碍与减少运动 ---------- */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  border: 0;
  clip: rect(0 0 0 0);
  overflow: hidden;
  white-space: nowrap;
}