/* =========================================================
   凤凰装点 · 全站共享样式 /assets/site.css
   ========================================================= */

/* ---------- 设计变量 ---------- */
:root {
  --color-primary: #FF3E00;
  --color-primary-dark: #C62A00;
  --color-bg: #0B0B0B;
  --color-surface: #1C1C1C;
  --color-surface-2: #242424;
  --color-accent: #FFB800;
  --color-text: #FFFFFF;
  --color-muted: #9A9A9A;
  --color-border: #2E2E2E;

  --font-heading: "Noto Sans SC", "PingFang SC", sans-serif;
  --font-body: "Noto Sans SC", "Microsoft YaHei", sans-serif;

  --text-sm: 14px;
  --text-base: 16px;
  --text-lg: 20px;

  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-5: 48px;
  --space-6: 64px;
  --space-7: 96px;

  --container-max: 1240px;
  --header-top-h: 38px;
  --header-main-h: 76px;
  --header-total-h: calc(var(--header-top-h) + var(--header-main-h));
  --radius: 0px;

  --ease-out: cubic-bezier(0.22, 0.61, 0.36, 1);
  --speed: 0.24s;
}

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

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

body,
h1,
h2,
h3,
h4,
h5,
h6,
p,
figure,
blockquote,
dl,
dd,
ul,
ol {
  margin: 0;
  padding: 0;
}

ul[class],
ol[class] {
  list-style: none;
}

main {
  display: block;
}

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

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

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

hr {
  border: none;
  border-top: 1px solid var(--color-border);
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--speed) var(--ease-out);
}

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

:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
}

::selection {
  background: var(--color-primary);
  color: #fff;
}

/* ---------- 基础排版 ---------- */
body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.75;
  color: var(--color-text);
  background-color: var(--color-bg);
  background-image: radial-gradient(ellipse 60% 40% at 85% -10%, rgba(255, 62, 0, 0.07), transparent 60%);
  background-repeat: no-repeat;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1,
h2,
h3,
h4 {
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  line-height: 1.2;
  letter-spacing: 0.01em;
  color: var(--color-text);
}

h1 {
  font-size: clamp(32px, 4.5vw, 52px);
}

h2 {
  font-size: clamp(26px, 3.2vw, 38px);
}

h3 {
  font-size: clamp(20px, 2.2vw, 26px);
}

h4 {
  font-size: 18px;
}

p {
  line-height: 1.75;
}

#main-content:focus {
  outline: none;
}

/* ---------- 布局容器 ---------- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--space-3);
}

.section {
  padding-block: var(--space-6);
}

.section--tight {
  padding-block: var(--space-4);
}

.section--bleed {
  padding-inline: 0;
}

/* ---------- 阅读进度 ---------- */
.scroll-progress {
  position: absolute;
  left: 0;
  bottom: -3px;
  width: 100%;
  height: 3px;
  background: transparent;
  pointer-events: none;
  z-index: 5;
}

.scroll-progress__bar {
  display: block;
  width: 0%;
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  box-shadow: 0 0 8px rgba(255, 62, 0, 0.45);
}

/* ---------- 跳过链接 ---------- */
.skip-link {
  position: absolute;
  top: 0;
  left: 0;
  z-index: 3000;
  display: inline-block;
  padding: 10px 20px;
  background: var(--color-accent);
  color: #111;
  font-size: var(--text-sm);
  font-weight: 700;
  letter-spacing: 0.04em;
  transform: translateY(-130%);
  transition: transform 0.2s var(--ease-out);
}

.skip-link:focus,
.skip-link:focus-visible {
  transform: translateY(0);
  outline: none;
  box-shadow: 0 0 0 2px var(--color-bg), 0 0 0 4px var(--color-accent);
}

/* ---------- 头部 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(11, 11, 11, 0.9);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-border);
}

.header-top {
  height: var(--header-top-h);
  background: linear-gradient(90deg, rgba(255, 62, 0, 0.08), transparent 60%);
  border-bottom: 1px solid var(--color-border);
}

.header-top-inner {
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--space-3);
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  font-size: 13px;
  color: var(--color-muted);
  letter-spacing: 0.05em;
}

.header-top-tagline {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  white-space: nowrap;
  color: var(--color-muted);
}

.header-top-tagline::before {
  content: '';
  width: 6px;
  height: 6px;
  background: var(--color-primary);
  transform: rotate(45deg);
  box-shadow: 0 0 8px rgba(255, 62, 0, 0.7);
}

.header-top-note {
  white-space: nowrap;
  font-size: 12px;
  color: var(--color-muted);
}

.header-main {
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--space-3);
  height: var(--header-main-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}

/* 品牌 */
.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
  color: var(--color-text);
}

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

.brand-mark {
  position: relative;
  display: inline-block;
  width: 34px;
  height: 38px;
  flex-shrink: 0;
}

.brand-mark::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(160deg, var(--color-accent) 5%, var(--color-primary) 45%, var(--color-primary-dark) 100%);
  clip-path: polygon(50% 0%, 100% 55%, 78% 92%, 50% 64%, 22% 92%, 0% 55%);
  transform: skewX(-10deg);
}

.brand-mark::after {
  content: '';
  position: absolute;
  top: 42%;
  left: 38%;
  width: 24%;
  height: 32%;
  background: var(--color-bg);
  clip-path: polygon(50% 0%, 100% 100%, 0 100%);
  transform: skewX(-10deg);
}

.brand-name {
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: 22px;
  letter-spacing: 0.04em;
  line-height: 1;
  white-space: nowrap;
}

.brand-name em {
  font-style: italic;
  color: var(--color-primary);
}

/* 主导航 */
.site-nav {
  flex: 1;
  display: flex;
  justify-content: center;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 4px;
}

.nav-item {
  position: relative;
}

.nav-link {
  display: inline-block;
  padding: 8px 14px;
  font-family: var(--font-heading);
  font-weight: 500;
  font-size: 15px;
  letter-spacing: 0.03em;
  color: var(--color-muted);
  position: relative;
  transition: color var(--speed) var(--ease-out);
}

.nav-link::after {
  content: '';
  position: absolute;
  left: 14px;
  right: 14px;
  bottom: 3px;
  height: 2px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform var(--speed) var(--ease-out);
}

.nav-link:hover,
.nav-link[aria-current="page"] {
  color: var(--color-text);
}

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

/* 头部 CTA */
.header-cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  flex-shrink: 0;
  background: var(--color-primary);
  color: #fff;
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  padding: 11px 24px;
  clip-path: polygon(0 0, calc(100% - 10px) 0, 100% 50%, calc(100% - 10px) 100%, 0 100%);
  transition: background var(--speed) var(--ease-out), transform var(--speed) var(--ease-out);
}

.header-cta::before {
  content: "\2193";
  font-style: normal;
  font-size: 16px;
  line-height: 1;
  transition: transform var(--speed) var(--ease-out);
}

.header-cta:hover {
  background: var(--color-primary-dark);
  color: #fff;
  transform: translateY(-1px);
}

.header-cta:hover::before {
  transform: translateY(2px);
}

/* 移动导航开关 */
.nav-toggle {
  display: none;
  flex-shrink: 0;
  width: 44px;
  height: 44px;
  padding: 10px;
  background: transparent;
  border: 1px solid var(--color-border);
  cursor: pointer;
  transition: border-color var(--speed) var(--ease-out);
}

.nav-toggle:hover {
  border-color: var(--color-primary);
}

.nav-toggle-bar {
  display: block;
  width: 20px;
  height: 2px;
  margin: 4px auto;
  background: var(--color-text);
  transition: transform var(--speed) var(--ease-out), opacity var(--speed) var(--ease-out);
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(1) {
  transform: translateY(6px) 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(-6px) rotate(-45deg);
}

/* ---------- 页脚 ---------- */
.site-footer {
  position: relative;
  background: var(--color-surface);
  border-top: 3px solid var(--color-primary);
  margin-top: var(--space-7);
}

.site-footer::before {
  content: '';
  position: absolute;
  top: -3px;
  left: 0;
  width: 180px;
  height: 3px;
  background: var(--color-accent);
  z-index: 1;
}

.footer-inner {
  display: grid;
  grid-template-columns: 1.7fr 1fr 1.3fr;
  gap: var(--space-5);
  padding-block: var(--space-6) var(--space-5);
}

.footer-brand-block {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.footer-trust {
  font-size: var(--text-sm);
  line-height: 1.8;
  color: var(--color-muted);
  max-width: 38em;
}

.footer-col {
  min-width: 0;
}

.footer-heading {
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: 16px;
  letter-spacing: 0.08em;
  color: var(--color-text);
  padding-bottom: 10px;
  border-bottom: 1px solid var(--color-border);
  position: relative;
}

.footer-heading::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 0;
  width: 32px;
  height: 2px;
  background: var(--color-primary);
}

.footer-links {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-top: var(--space-2);
}

.footer-links a {
  display: inline-block;
  position: relative;
  padding-left: 20px;
  color: var(--color-muted);
  font-size: var(--text-sm);
  line-height: 1.6;
  transition: color var(--speed) var(--ease-out), transform var(--speed) var(--ease-out);
}

.footer-links a::before {
  content: "\2192";
  position: absolute;
  left: 0;
  top: 0;
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  color: var(--color-border);
  transition: color var(--speed) var(--ease-out), left var(--speed) var(--ease-out);
}

.footer-links a:hover {
  color: var(--color-primary);
  transform: translateX(2px);
}

.footer-links a:hover::before {
  color: var(--color-primary);
  left: 2px;
}

.footer-contact-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-top: var(--space-2);
}

.footer-contact-list li {
  display: flex;
  gap: 10px;
  font-size: var(--text-sm);
  line-height: 1.6;
}

.contact-key {
  flex-shrink: 0;
  min-width: 40px;
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: 13px;
  color: var(--color-accent);
}

.contact-value {
  color: var(--color-muted);
  word-break: break-all;
}

.footer-bottom {
  background: #131313;
  border-top: 1px solid var(--color-border);
}

.footer-bottom-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
  padding-block: 16px;
  font-size: 13px;
  color: var(--color-muted);
}

.footer-bottom-inner p {
  line-height: 1.5;
}

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 28px;
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: 15px;
  letter-spacing: 0.04em;
  border: 1px solid transparent;
  cursor: pointer;
  background: transparent;
  color: var(--color-text);
  transition: background var(--speed) var(--ease-out), color var(--speed) var(--ease-out), border-color var(--speed) var(--ease-out), transform var(--speed) var(--ease-out);
}

.btn-primary {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
  padding-right: 30px;
  clip-path: polygon(0 0, calc(100% - 12px) 0, 100% 50%, calc(100% - 12px) 100%, 0 100%);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  border-color: var(--color-primary-dark);
  color: #fff;
  transform: translateY(-1px);
}

.btn-outline {
  border-color: var(--color-border);
  color: var(--color-text);
}

.btn-outline:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  background: rgba(255, 62, 0, 0.06);
}

/* ---------- 卡片面板 ---------- */
.panel {
  position: relative;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  padding: var(--space-4);
  transition: border-color var(--speed) var(--ease-out), background var(--speed) var(--ease-out), transform var(--speed) var(--ease-out);
}

.panel:hover {
  border-color: rgba(255, 62, 0, 0.55);
  background: var(--color-surface-2);
}

.panel--feature {
  border-top: 3px solid var(--color-primary);
}

.panel--dark {
  background: #141414;
}

.panel-title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: 20px;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}

.panel-copy {
  color: var(--color-muted);
  font-size: 15px;
}

/* ---------- 标签 ---------- */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 5px 14px;
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: 13px;
  letter-spacing: 0.06em;
  color: var(--color-accent);
  background: transparent;
  border: 1px solid var(--color-border);
}

.tag::before {
  content: '';
  width: 4px;
  height: 4px;
  background: currentColor;
  transform: rotate(45deg);
}

.tag--solid {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
}

.tag--solid::before {
  background: #fff;
}

.tag--gold {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: #111;
}

.tag--gold::before {
  background: #111;
}

/* ---------- 数据统计 ---------- */
.spec-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--space-4);
}

.spec {
  position: relative;
  padding: var(--space-3) var(--space-3) var(--space-3) var(--space-4);
  background: var(--color-surface);
  border-left: 3px solid var(--color-primary);
  overflow: hidden;
}

.spec::after {
  content: '';
  position: absolute;
  right: -12px;
  bottom: -12px;
  width: 48px;
  height: 48px;
  border: 1px solid var(--color-border);
  transform: rotate(45deg);
}

.spec-figure {
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: clamp(30px, 3.4vw, 42px);
  line-height: 1.1;
  color: var(--color-text);
}

.spec-figure em {
  color: var(--color-accent);
  font-style: italic;
  font-size: 0.72em;
  margin-left: 2px;
}

.spec-label {
  margin-top: 6px;
  padding-top: 6px;
  border-top: 1px solid var(--color-border);
  font-size: 13px;
  letter-spacing: 0.06em;
  color: var(--color-muted);
}

/* ---------- 章节系统 ---------- */
.chapter {
  position: relative;
  padding-block: var(--space-5);
  border-top: 1px solid var(--color-border);
  transition: border-color var(--speed) var(--ease-out);
}

.chapter::before {
  content: '';
  position: absolute;
  top: -1px;
  left: 0;
  width: 100%;
  height: 3px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.45s var(--ease-out);
}

.chapter.is-active::before {
  transform: scaleX(1);
}

.chapter-meta {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin-bottom: var(--space-2);
}

.chapter-num {
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: clamp(44px, 5vw, 64px);
  line-height: 1;
  color: transparent;
  -webkit-text-stroke: 1px rgba(255, 62, 0, 0.4);
  letter-spacing: 0.02em;
}

.chapter-tag {
  font-size: 13px;
  letter-spacing: 0.14em;
  color: var(--color-muted);
  text-transform: uppercase;
  border-left: 2px solid var(--color-primary);
  padding-left: 10px;
  line-height: 1.4;
}

.chapter-title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: clamp(22px, 2.8vw, 30px);
  color: var(--color-text);
  margin-bottom: var(--space-3);
  max-width: 22em;
}

/* ---------- 图片容器 ---------- */
.img-frame {
  position: relative;
  overflow: hidden;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
}

.img-frame--16x9 {
  aspect-ratio: 16 / 9;
}

.img-frame--4x3 {
  aspect-ratio: 4 / 3;
}

.img-frame--1x1 {
  aspect-ratio: 1 / 1;
}

.img-frame--3x2 {
  aspect-ratio: 3 / 2;
}

.img-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s var(--ease-out);
}

.img-frame:hover img {
  transform: scale(1.03);
}

.img-frame::after {
  content: "";
  position: absolute;
  inset: 0;
  border: 1px solid rgba(255, 255, 255, 0.06);
  pointer-events: none;
}

/* ---------- 面包屑 ---------- */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  padding-block: 14px;
  font-size: var(--text-sm);
  color: var(--color-muted);
}

.breadcrumb a {
  color: var(--color-muted);
}

.breadcrumb a:hover {
  color: var(--color-primary);
}

.breadcrumb-sep {
  color: var(--color-border);
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: 12px;
}

.breadcrumb [aria-current="page"] {
  color: var(--color-text);
  font-weight: 500;
}

/* ---------- 内页首屏 ---------- */
.page-hero {
  position: relative;
  padding-block: var(--space-6) var(--space-5);
  border-bottom: 1px solid var(--color-border);
  background: linear-gradient(180deg, rgba(255, 62, 0, 0.07), transparent 80%), var(--color-bg);
  overflow: hidden;
}

.page-hero::after {
  content: '';
  position: absolute;
  top: 0;
  right: 0;
  width: 38vw;
  height: 100%;
  background: linear-gradient(135deg, transparent 55%, rgba(255, 184, 0, 0.06) 100%);
  pointer-events: none;
}

.page-hero-kicker {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  letter-spacing: 0.14em;
  color: var(--color-accent);
  text-transform: uppercase;
  margin-bottom: var(--space-2);
}

.page-hero-kicker::before {
  content: '';
  width: 32px;
  height: 2px;
  background: var(--color-primary);
}

.page-hero-title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-style: italic;
  font-size: clamp(30px, 4.2vw, 46px);
  line-height: 1.12;
  max-width: 16em;
}

.page-hero-sub {
  margin-top: var(--space-2);
  color: var(--color-muted);
  max-width: 34em;
  font-size: var(--text-base);
}

/* ---------- 正文排版 ---------- */
.prose {
  max-width: 72ch;
  color: rgba(255, 255, 255, 0.85);
  font-size: var(--text-base);
}

.prose > * + * {
  margin-top: 1em;
}

.prose h2 {
  font-size: 24px;
  margin-top: 1.6em;
  padding-bottom: 0.4em;
  border-bottom: 1px solid var(--color-border);
}

.prose h3 {
  font-size: 20px;
  margin-top: 1.4em;
}

.prose ul,
.prose ol {
  padding-left: 1.4em;
}

.prose ul li {
  list-style: disc;
}

.prose ol li {
  list-style: decimal;
}

.prose strong {
  color: var(--color-accent);
  font-weight: 700;
}

.prose a {
  color: var(--color-primary);
  text-decoration: underline;
  text-underline-offset: 3px;
}

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

.prose blockquote {
  border-left: 3px solid var(--color-primary);
  padding: 0.2em 0 0.2em 20px;
  color: var(--color-muted);
  font-style: italic;
  margin-block: 1.5em;
}

/* ---------- 栅格 ---------- */
.row {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: var(--space-4);
}

.col-span-3 {
  grid-column: span 3;
}

.col-span-4 {
  grid-column: span 4;
}

.col-span-5 {
  grid-column: span 5;
}

.col-span-6 {
  grid-column: span 6;
}

.col-span-7 {
  grid-column: span 7;
}

.col-span-8 {
  grid-column: span 8;
}

.col-span-9 {
  grid-column: span 9;
}

.col-span-12 {
  grid-column: span 12;
}

/* ---------- 装饰与分隔 ---------- */
.divider {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: var(--space-5) 0;
}

.divider--accent {
  border-top: 3px solid var(--color-primary);
  width: 64px;
  margin: var(--space-4) 0;
}

.slash {
  display: inline-block;
  width: 44px;
  height: 2px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  transform: skewX(-18deg);
}

/* ---------- 滚动显现 ---------- */
.js-enabled [data-reveal] {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s var(--ease-out), transform 0.6s var(--ease-out);
}

.js-enabled [data-reveal].is-revealed {
  opacity: 1;
  transform: translateY(0);
}

/* ---------- 移动端响应 ---------- */
@media (max-width: 1024px) {
  .nav-toggle {
    display: block;
  }

  .site-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: rgba(11, 11, 11, 0.98);
    -webkit-backdrop-filter: blur(12px);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
    box-shadow: 0 32px 48px rgba(0, 0, 0, 0.5);
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s var(--ease-out);
  }

  .site-nav[data-open] {
    max-height: calc(100vh - var(--header-total-h));
    overflow-y: auto;
  }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: var(--space-2) var(--space-3) var(--space-3);
  }

  .nav-item {
    border-bottom: 1px solid var(--color-border);
  }

  .nav-item:last-child {
    border-bottom: none;
  }

  .nav-link {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 4px;
    font-size: 17px;
    font-weight: 700;
  }

  .nav-link::after {
    display: none;
  }

  .nav-link[aria-current="page"] {
    color: var(--color-primary);
  }

  .col-span-3,
  .col-span-4,
  .col-span-5 {
    grid-column: span 6;
  }

  .col-span-7,
  .col-span-8,
  .col-span-9 {
    grid-column: span 12;
  }

  .footer-inner {
    grid-template-columns: 1fr 1fr;
  }

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

@media (max-width: 640px) {
  :root {
    --header-top-h: 34px;
    --header-main-h: 64px;
  }

  .header-top-note {
    display: none;
  }

  .brand-mark {
    width: 28px;
    height: 32px;
  }

  .brand-name {
    font-size: 18px;
  }

  .brand {
    gap: 8px;
  }

  .header-cta {
    padding: 10px 14px;
    font-size: 13px;
  }

  .header-cta::before {
    font-size: 14px;
  }

  .header-main {
    gap: var(--space-2);
  }

  .col-span-3,
  .col-span-4,
  .col-span-5,
  .col-span-6 {
    grid-column: span 12;
  }

  .footer-inner {
    grid-template-columns: 1fr;
    gap: var(--space-4);
    padding-block: var(--space-5) var(--space-4);
  }

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

  .footer-bottom-inner {
    flex-direction: column;
    align-items: flex-start;
    gap: 4px;
  }

  .page-hero {
    padding-block: var(--space-5) var(--space-4);
  }
}

/* ---------- 减弱动效 ---------- */
@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;
  }

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

  .chapter::before {
    transform: scaleX(1);
  }
}