/* ===== 变量与重置 ===== */
:root {
  --bg-deep: #0A0E17;
  --bg-raised: #111A24;
  --neon-green: #00E68C;
  --electric-blue: #00A6FF;
  --gold: #FFB800;
  --danger: #FF4D4F;
  --success: #00C853;
  --text-main: #F2F6FC;
  --text-sub: #9AA7B8;
  --border-c: #1E2A38;
  --font-display: 'Archivo', 'Noto Sans SC', 'Microsoft YaHei', 'PingFang SC', sans-serif;
  --font-body: 'Noto Sans SC', 'Microsoft YaHei', 'PingFang SC', sans-serif;
  --font-mono: 'Roboto Mono', 'JetBrains Mono', 'SFMono-Regular', Consolas, monospace;
  --container-w: 1280px;
  --header-h: 72px;
  --space-sec: clamp(4rem, 8vw, 7rem);
}

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background-color: var(--bg-deep);
  color: var(--text-main);
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.75;
  overflow-x: hidden;
}

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

a {
  color: var(--electric-blue);
}

ul, ol {
  list-style: none;
}

button {
  font: inherit;
  color: inherit;
  background: none;
  border: none;
  cursor: pointer;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 1.5rem;
}

th, td {
  text-align: left;
  padding: .75rem 1rem;
  border-bottom: 2px solid var(--border-c);
  font-size: .92rem;
}

th {
  font-family: var(--font-display);
  font-weight: 700;
  color: var(--neon-green);
  white-space: nowrap;
}

td {
  color: var(--text-sub);
}

blockquote {
  border-inline-start: 4px solid var(--neon-green);
  padding: 1rem 1.5rem;
  margin: 2rem 0;
  background: var(--bg-raised);
  color: var(--text-sub);
  font-style: italic;
}

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 800;
  line-height: 1.15;
  color: var(--text-main);
  text-wrap: balance;
}

:focus-visible {
  outline: 3px solid var(--electric-blue);
  outline-offset: 2px;
  border-radius: 2px;
}

::selection {
  background: var(--neon-green);
  color: var(--bg-deep);
}

::-webkit-scrollbar {
  width: 10px;
}

::-webkit-scrollbar-track {
  background: var(--bg-deep);
}

::-webkit-scrollbar-thumb {
  background: var(--electric-blue);
  border: 2px solid var(--bg-deep);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--neon-green);
}

[id], [data-board] {
  scroll-margin-top: calc(var(--header-h) + 1rem);
}

/* ===== 布局工具 ===== */
.container {
  width: 100%;
  max-width: var(--container-w);
  margin-inline: auto;
  padding-inline: clamp(1rem, 4vw, 2.5rem);
}

.main-content {
  flex: 1;
  width: 100%;
}

.section {
  padding-block: var(--space-sec);
  position: relative;
}

.section--alt {
  background: var(--bg-raised);
  border-block: 2px solid var(--border-c);
}

.section__inner {
  display: grid;
  grid-template-columns: minmax(0, 240px) minmax(0, 1fr);
  gap: clamp(2rem, 5vw, 4.5rem);
}

.section__content {
  min-width: 0;
}

.grid {
  display: grid;
  gap: clamp(1.25rem, 3vw, 2rem);
}

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

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

.grid--asym {
  grid-template-columns: 1.2fr .8fr;
}

.grid-overlay {
  background-image:
    linear-gradient(rgba(255,255,255,.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.03) 1px, transparent 1px);
  background-size: 40px 40px;
}

.visually-hidden {
  position: absolute !important;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  border: 0;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  overflow: hidden;
  white-space: nowrap;
}

/* ===== 标题与数字 ===== */
.section-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: .6rem;
  font-family: var(--font-mono);
  font-size: .8rem;
  font-weight: 600;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--neon-green);
}

.section-eyebrow::before {
  content: "";
  width: 28px;
  height: 2px;
  background: var(--neon-green);
}

.section-title {
  font-size: clamp(1.8rem, 4vw, 3rem);
  transform: skewX(-4deg);
  margin-top: .75rem;
  margin-bottom: 1rem;
}

.section-subtitle {
  color: var(--text-sub);
  max-width: 640px;
  margin-bottom: clamp(2rem, 4vw, 3rem);
}

.lead {
  font-size: 1.1rem;
  color: var(--text-sub);
}

.big-number {
  font-family: var(--font-mono);
  font-size: clamp(2.6rem, 8vw, 5.5rem);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -.04em;
  color: var(--neon-green);
  font-variant-numeric: tabular-nums;
}

.big-number--blue {
  color: var(--electric-blue);
}

.big-number--gold {
  color: var(--gold);
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: .35rem;
  font-family: var(--font-mono);
  font-size: .75rem;
  font-weight: 600;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--text-sub);
  border: 1px solid var(--border-c);
  padding: .3rem .65rem;
  white-space: nowrap;
}

.tag--green {
  color: var(--neon-green);
  border-color: var(--neon-green);
}

.tag--blue {
  color: var(--electric-blue);
  border-color: var(--electric-blue);
}

.tag--gold {
  color: var(--gold);
  border-color: var(--gold);
}

/* ===== 按钮 ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: .6rem;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: .95rem;
  padding: .8rem 1.6rem;
  text-decoration: none;
  border: 2px solid transparent;
  transition: background-color .25s, border-color .25s, color .25s, transform .25s, box-shadow .25s;
  cursor: pointer;
}

.btn--primary {
  background: var(--neon-green);
  color: var(--bg-deep);
  transform: skewX(-6deg);
  box-shadow: 4px 4px 0 0 rgba(0, 230, 140, .25);
}

.btn--primary:hover {
  background: var(--electric-blue);
  box-shadow: 4px 4px 0 0 rgba(0, 166, 255, .3);
  transform: skewX(-6deg) translateY(-2px);
}

.btn--ghost {
  border-color: var(--electric-blue);
  color: var(--electric-blue);
}

.btn--ghost:hover {
  background: var(--electric-blue);
  color: var(--bg-deep);
}

.btn--sm {
  padding: .5rem 1rem;
  font-size: .85rem;
}

/* ===== 头部 ===== */
.site-header {
  position: fixed;
  inset-inline: 0;
  top: 0;
  z-index: 100;
  border-bottom: 1px solid transparent;
  transition: background-color .3s, border-color .3s, box-shadow .3s;
}

.site-header.is-scrolled {
  background: rgba(10, 14, 23, .9);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom-color: var(--border-c);
  box-shadow: 0 8px 24px rgba(0, 0, 0, .35);
}

.site-header__inner {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  height: var(--header-h);
  max-width: var(--container-w);
  margin-inline: auto;
  padding-inline: clamp(1rem, 4vw, 2.5rem);
}

.site-header__brand {
  display: inline-flex;
  align-items: center;
  gap: .6rem;
  margin-inline-end: auto;
  text-decoration: none;
  color: var(--text-main);
  font-family: var(--font-display);
}

.site-header__brand-mark {
  font-family: var(--font-mono);
  font-weight: 800;
  font-size: 1.35rem;
  letter-spacing: -.03em;
  transform: skewX(-6deg);
  background: linear-gradient(135deg, var(--neon-green), var(--electric-blue));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

.site-header__brand-text {
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: .04em;
}

.site-nav {
  display: flex;
  align-items: center;
}

.site-nav__list {
  display: flex;
  align-items: center;
  gap: clamp(.75rem, 2vw, 1.75rem);
}

.site-nav a {
  position: relative;
  display: inline-block;
  font-family: var(--font-display);
  font-size: .92rem;
  font-weight: 600;
  color: var(--text-sub);
  text-decoration: none;
  padding-block: .25rem;
  transition: color .2s;
}

.site-nav a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -4px;
  width: 100%;
  height: 2px;
  background: var(--neon-green);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform .25s;
}

.site-nav a:hover {
  color: var(--text-main);
}

.site-nav a:hover::after {
  transform: scaleX(1);
}

.site-nav a[aria-current="page"] {
  color: var(--neon-green);
}

.site-nav a[aria-current="page"]::after {
  transform: scaleX(1);
}

.btn-header-cta {
  display: inline-flex;
  align-items: center;
  gap: .5rem;
  font-family: var(--font-display);
  font-size: .88rem;
  font-weight: 800;
  color: var(--bg-deep);
  background: var(--neon-green);
  text-decoration: none;
  padding: .55rem 1.2rem;
  transform: skewX(-6deg);
  box-shadow: 4px 4px 0 0 rgba(0, 230, 140, .25);
  transition: background-color .25s, box-shadow .25s, transform .25s;
}

.btn-header-cta:hover {
  background: var(--electric-blue);
  box-shadow: 4px 4px 0 0 rgba(0, 166, 255, .3);
  transform: skewX(-6deg) translateY(-1px);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 5px;
  width: 42px;
  height: 42px;
  border: 2px solid var(--border-c);
  background: rgba(17, 26, 36, .6);
  padding: 0 10px;
}

.nav-toggle__bar {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--text-main);
  transition: transform .3s, opacity .3s;
}

.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

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

.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

.skip-link {
  position: fixed;
  top: 0;
  left: 1rem;
  z-index: 300;
  transform: translateY(-120%);
  background: var(--neon-green);
  color: var(--bg-deep);
  font-weight: 700;
  font-size: .9rem;
  padding: .7rem 1.4rem;
  text-decoration: none;
  box-shadow: 4px 4px 0 0 rgba(0, 0, 0, .4);
  transition: transform .25s;
}

.skip-link:focus {
  transform: translateY(0);
}

.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 0%;
  background: linear-gradient(to right, var(--neon-green), var(--electric-blue));
  z-index: 200;
  pointer-events: none;
}

.back-top {
  position: fixed;
  right: 1.25rem;
  bottom: 1.25rem;
  z-index: 90;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--bg-deep);
  background: var(--neon-green);
  border: 2px solid var(--neon-green);
  box-shadow: 4px 4px 0 0 rgba(0, 230, 140, .3);
  font-size: 1.2rem;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: opacity .3s, visibility .3s, transform .3s, background-color .3s;
}

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

.back-top:hover {
  background: var(--electric-blue);
  border-color: var(--electric-blue);
}

/* ===== 页脚 ===== */
.site-footer {
  background: var(--bg-raised);
  border-top: 2px solid var(--border-c);
}

.site-footer__brace {
  height: 4px;
  background:
    repeating-linear-gradient(90deg,
      var(--neon-green) 0 56px,
      var(--electric-blue) 56px 88px,
      transparent 88px 128px);
}

.site-footer__grid {
  display: grid;
  grid-template-columns: 1.4fr .8fr 1fr;
  gap: clamp(2rem, 5vw, 4rem);
  padding-block: clamp(2.5rem, 5vw, 4rem);
}

.site-footer__brand {
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  text-decoration: none;
}

.site-footer__brand-en {
  font-family: var(--font-mono);
  font-weight: 800;
  font-size: 1.35rem;
  letter-spacing: -.03em;
  background: linear-gradient(135deg, var(--neon-green), var(--electric-blue));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

.site-footer__brand-zh {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.05rem;
  letter-spacing: .05em;
  color: var(--text-main);
}

.site-footer__trust {
  color: var(--text-sub);
  font-size: .92rem;
  max-width: 40em;
  margin-top: 1rem;
}

.site-footer__meta {
  display: flex;
  flex-wrap: wrap;
  gap: .5rem;
  margin-top: 1.25rem;
}

.site-footer__heading {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: .1em;
  color: var(--text-main);
  text-transform: uppercase;
  margin-bottom: 1rem;
  padding-bottom: .5rem;
  border-bottom: 2px solid var(--border-c);
}

.site-footer__list {
  display: grid;
  gap: .6rem;
  font-size: .92rem;
}

.site-footer__list a {
  color: var(--text-sub);
  text-decoration: none;
  transition: color .2s;
}

.site-footer__list a:hover {
  color: var(--neon-green);
}

.site-footer__list--contact {
  color: var(--text-sub);
}

.site-footer__note {
  margin-top: 1rem;
  font-size: .85rem;
  color: var(--text-sub);
  opacity: .85;
}

.site-footer__bottom {
  border-top: 2px solid var(--border-c);
  padding-block: 1.1rem;
}

.site-footer__bottom-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .5rem 1.5rem;
  font-size: .85rem;
  color: var(--text-sub);
}

.site-footer__icp {
  font-family: var(--font-mono);
}

.site-footer__legal {
  display: flex;
  gap: 1.5rem;
  margin-inline-start: auto;
}

.site-footer__legal a {
  color: var(--text-sub);
  text-decoration: none;
  transition: color .2s;
}

.site-footer__legal a:hover {
  color: var(--electric-blue);
}

/* ===== 页面首屏与面包屑 ===== */
.page-hero {
  padding-top: calc(var(--header-h) + clamp(2rem, 6vw, 4rem));
  padding-bottom: clamp(2rem, 5vw, 4rem);
  border-bottom: 2px solid var(--border-c);
  background:
    radial-gradient(ellipse 60% 50% at 85% 20%, rgba(0, 166, 255, .14), transparent),
    radial-gradient(ellipse 40% 60% at 10% 90%, rgba(0, 230, 140, .1), transparent);
}

.page-hero__title {
  font-size: clamp(2.2rem, 6vw, 4rem);
  transform: skewX(-4deg);
  margin-top: .75rem;
}

.page-hero__lead {
  color: var(--text-sub);
  max-width: 640px;
  margin-top: 1rem;
  font-size: 1.05rem;
}

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .5rem;
  font-size: .9rem;
  color: var(--text-sub);
}

.breadcrumb a {
  color: var(--electric-blue);
  text-decoration: none;
}

.breadcrumb a:hover {
  text-decoration: underline;
}

.breadcrumb__sep {
  color: var(--text-sub);
  opacity: .6;
  font-family: var(--font-mono);
}

.breadcrumb [aria-current="page"] {
  color: var(--text-main);
}

/* ===== 卡片与研究板 ===== */
.board {
  position: relative;
  background: var(--bg-raised);
  border: 2px solid var(--border-c);
}

.board::before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: 4px;
  background: linear-gradient(180deg, var(--neon-green), var(--electric-blue));
}

.board__header {
  display: flex;
  align-items: center;
  gap: .75rem;
  padding: 1.1rem 1.4rem;
  border-bottom: 2px solid var(--border-c);
}

.board__title {
  font-size: 1.05rem;
  font-weight: 800;
}

.board__body {
  padding: 1.4rem;
}

.board__footer {
  padding: .9rem 1.4rem;
  border-top: 2px solid var(--border-c);
  color: var(--text-sub);
  font-size: .85rem;
}

.card {
  background: var(--bg-raised);
  border: 2px solid var(--border-c);
  padding: 1.5rem;
  transition: border-color .25s, transform .25s, box-shadow .25s;
}

.card:hover {
  border-color: var(--electric-blue);
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(0, 0, 0, .25);
}

.card__header {
  margin-bottom: 1rem;
}

.card__body {
  color: var(--text-sub);
  font-size: .92rem;
}

.card__footer {
  margin-top: 1.25rem;
}

/* ===== 数据条 ===== */
.progress-bar {
  height: 10px;
  background: var(--bg-deep);
  border: 1px solid var(--border-c);
  position: relative;
  overflow: hidden;
}

.progress-bar__fill {
  display: block;
  height: 100%;
  width: 0%;
  background: repeating-linear-gradient(90deg, var(--neon-green) 0 12px, rgba(0, 230, 140, .4) 12px 16px);
  transition: width .6s ease;
}

.progress-bar--blue .progress-bar__fill {
  background: repeating-linear-gradient(90deg, var(--electric-blue) 0 12px, rgba(0, 166, 255, .4) 12px 16px);
}

.progress-bar--gold .progress-bar__fill {
  background: repeating-linear-gradient(90deg, var(--gold) 0 12px, rgba(255, 184, 0, .4) 12px 16px);
}

/* ===== 图片容器 ===== */
.img-frame {
  position: relative;
  overflow: hidden;
  background: var(--bg-raised);
  border: 2px solid var(--border-c);
  aspect-ratio: 16 / 10;
}

.img-frame--wide {
  aspect-ratio: 21 / 9;
}

.img-frame--tall {
  aspect-ratio: 4 / 5;
}

.img-frame--square {
  aspect-ratio: 1;
}

.img-frame img,
.img-frame svg,
.img-frame__media {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.img-frame__caption {
  position: absolute;
  inset-inline: 0;
  bottom: 0;
  padding: .5rem 1rem;
  background: linear-gradient(transparent, rgba(10, 14, 23, .9));
  font-size: .85rem;
  color: var(--text-main);
  pointer-events: none;
}

/* ===== 手风琴 ===== */
.accordion {
  border: 2px solid var(--border-c);
  background: var(--bg-raised);
}

.accordion__item + .accordion__item {
  border-top: 2px solid var(--border-c);
}

.accordion__trigger {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: 1.1rem 1.25rem;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: .98rem;
  color: var(--text-main);
  text-align: left;
  transition: color .2s;
}

.accordion__trigger:hover {
  color: var(--electric-blue);
}

.accordion__icon {
  font-family: var(--font-mono);
  font-size: 1.3rem;
  color: var(--neon-green);
  transition: transform .3s;
}

.accordion__item[data-open="true"] .accordion__icon {
  transform: rotate(45deg);
}

.js .accordion__panel {
  display: none;
  padding: 0 1.25rem 1.25rem;
  color: var(--text-sub);
  font-size: .95rem;
}

.js .accordion__item[data-open="true"] .accordion__panel {
  display: block;
}

/* ===== 动态列表 ===== */
.news-list li {
  padding-block: 1.25rem;
  border-bottom: 2px solid var(--border-c);
}

.news-list li:first-child {
  padding-top: 0;
}

.news-list a {
  display: block;
  color: var(--text-main);
  text-decoration: none;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.05rem;
  transition: color .2s;
}

.news-list a:hover {
  color: var(--neon-green);
}

.news-list time {
  display: block;
  font-family: var(--font-mono);
  font-size: .82rem;
  color: var(--electric-blue);
  margin-bottom: .35rem;
}

/* ===== 章节导航 ===== */
.chapter-nav {
  position: sticky;
  top: calc(var(--header-h) + 1.5rem);
}

.chapter-nav a {
  display: flex;
  align-items: center;
  gap: .5rem;
  font-size: .9rem;
  font-weight: 600;
  color: var(--text-sub);
  text-decoration: none;
  padding: .4rem 0;
  transition: color .2s;
}

.chapter-nav a::before {
  content: "";
  width: 6px;
  height: 6px;
  background: var(--electric-blue);
  transform: skewX(-10deg);
  opacity: .4;
  transition: opacity .2s, background-color .2s;
}

.chapter-nav a:hover {
  color: var(--text-main);
}

.chapter-nav a.is-active {
  color: var(--neon-green);
}

.chapter-nav a.is-active::before {
  background: var(--neon-green);
  opacity: 1;
}

/* ===== 分页 ===== */
.pagination {
  display: flex;
  flex-wrap: wrap;
  gap: .5rem;
  margin-top: 2rem;
}

.pagination a,
.pagination span {
  display: inline-grid;
  place-items: center;
  min-width: 40px;
  height: 40px;
  padding-inline: .5rem;
  border: 2px solid var(--border-c);
  color: var(--text-sub);
  font-family: var(--font-mono);
  font-size: .9rem;
  font-weight: 600;
  text-decoration: none;
  transition: border-color .2s, color .2s, background-color .2s;
}

.pagination a:hover {
  border-color: var(--electric-blue);
  color: var(--electric-blue);
}

.pagination .is-current {
  border-color: var(--neon-green);
  background: var(--neon-green);
  color: var(--bg-deep);
}

/* ===== 正文与分隔 ===== */
.content-prose {
  max-width: 760px;
}

.content-prose p,
.content-prose ul,
.content-prose ol,
.content-prose table {
  margin-bottom: 1.5rem;
}

.content-prose ul {
  list-style: disc;
  padding-inline-start: 1.5rem;
}

.content-prose ol {
  list-style: decimal;
  padding-inline-start: 1.5rem;
}

.content-prose h2 {
  font-size: 1.7rem;
  margin-top: 3rem;
  margin-bottom: 1rem;
  transform: skewX(-3deg);
}

.content-prose h3 {
  font-size: 1.2rem;
  margin-top: 2rem;
  margin-bottom: .75rem;
}

.content-prose a {
  color: var(--electric-blue);
}

.divider {
  height: 2px;
  border: 0;
  background: var(--border-c);
  margin-block: 2rem;
}

.divider--neon {
  background: linear-gradient(90deg, var(--neon-green), transparent 80%);
  height: 2px;
  border: 0;
}

/* ===== 滚动显现 ===== */
.js [data-reveal] {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity .5s ease, transform .5s ease;
}

.js [data-reveal="done"] {
  opacity: 1;
  transform: none;
}

/* ===== 响应式 ===== */
@media (max-width: 1024px) {
  .site-footer__grid {
    grid-template-columns: 1fr 1fr;
  }

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

@media (max-width: 980px) {
  .grid--3 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 880px) {
  .nav-toggle {
    display: inline-flex;
  }

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

  .chapter-nav {
    position: static;
    display: flex;
    flex-wrap: wrap;
    gap: .25rem .75rem;
    border-inline-start: 0;
    border-bottom: 2px solid var(--border-c);
    padding: 0 0 .5rem;
    margin-bottom: 1.5rem;
  }

  .js .site-nav {
    position: fixed;
    top: var(--header-h);
    left: 0;
    right: 0;
    z-index: 99;
    flex-direction: column;
    align-items: stretch;
    background: rgba(10, 14, 23, .98);
    border-bottom: 2px solid var(--border-c);
    box-shadow: 0 16px 30px rgba(0, 0, 0, .45);
    padding: 0;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-12px);
    transition: opacity .3s, transform .3s, visibility .3s;
  }

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

  .site-nav__list {
    flex-wrap: wrap;
    row-gap: .25rem;
  }

  .js .site-nav__list {
    flex-direction: column;
    flex-wrap: nowrap;
    gap: 0;
    padding: .5rem clamp(1rem, 4vw, 2.5rem) 1rem;
  }

  .js .site-nav__item {
    width: 100%;
  }

  .js .site-nav a {
    display: block;
    font-size: 1.05rem;
    padding: .85rem 0;
    border-bottom: 1px solid rgba(30, 42, 56, .7);
  }
}

@media (max-width: 680px) {
  .grid--2,
  .grid--3,
  .grid--asym {
    grid-template-columns: 1fr;
  }

  .site-footer__grid {
    grid-template-columns: 1fr;
  }

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

  .site-footer__bottom-inner {
    flex-direction: column;
    align-items: flex-start;
  }

  .site-footer__legal {
    margin-inline-start: 0;
  }
}

@media (max-width: 480px) {
  .btn-header-cta {
    padding: .45rem .7rem;
    font-size: .78rem;
  }

  .site-header__brand-text {
    display: none;
  }

  .site-header__inner {
    gap: 1rem;
  }
}

/* ===== 降低动态偏好 ===== */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *, *::before, *::after {
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .01ms !important;
    transition-delay: 0s !important;
    scroll-behavior: auto !important;
  }

  .js [data-reveal] {
    opacity: 1;
    transform: none;
    transition: none;
  }
}