:root {
  --color-surface: #ffffff;
  --color-surface-alt: #f5f5f5;
  --color-surface-deep: #e7e7e7;
  --color-ink: #3b3536;
  --color-ink-soft: #685e60;
  --color-ink-muted: #857a7c;
  --color-line: #dcdbdb;
  --color-primary: #e71834;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #fcdfe3;
  --color-accent: #e7132f;
  --color-accent-ink: #ffffff;
  --color-highlight: #fbd5da;
  --color-focus: #ea0624;
  --color-contrast-surface: #210f12;
  --color-contrast-ink: #e7e4e5;
  --color-contrast-line: #4d3e40;
  --color-contrast-accent: #ee3049;
  --overlay-scrim: linear-gradient(180deg, rgba(33, 15, 18, 0.35) 0%, rgba(33, 15, 18, 0.72) 55%, rgba(33, 15, 18, 0.92) 100%);
  --font-heading: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-body: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --text-xs: 11.4px;
  --text-sm: 14.3px;
  --text-base: 16px;
  --text-lg: 20.0px;
  --text-xl: 25.0px;
  --text-2xl: 31.2px;
  --text-3xl: 39.1px;
  --text-4xl: 48.8px;
  --text-display: clamp(47px, 9.6vw, 123px);
  --text-figure: clamp(39px, 7.0vw, 89px);
  --weight-heading: 834;
  --weight-body: 400;
  --leading-body: 1.72;
  --leading-heading: 1.18;
  --tracking-heading: -0.019em;
  --radius-sm: 0px;
  --radius-md: 0px;
  --radius-lg: 0px;
  --radius-pill: 0px;
  --border-thin: 1px;
  --border-thick: 1px;
  --shadow-1: none;
  --shadow-2: none;
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1160px;
  --measure: 67ch;
  --gutter: 32px;
  --section-y: 105px;
  --section-y-lg: 147px;
}

/* ==========================================================================
   00 · 重置与中文排版基线
   ========================================================================== */
*,
*::before,
*::after { box-sizing: border-box; }

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

body {
  margin: 0;
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  letter-spacing: 0.01em;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

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

h1, h2, h3, h4, h5, h6 {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

p { margin: 0 0 var(--space-2); }
p:last-child { margin-bottom: 0; }
ul, ol { margin: 0; padding-left: 0; }
a { color: var(--color-primary); text-decoration-thickness: 1px; }
button { font: inherit; color: inherit; }
hr { margin: 0; border: 0; border-top: var(--border-thin) solid var(--color-line); }
main { display: block; }
[id] { scroll-margin-top: 108px; }

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

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

/* ==========================================================================
   01 · 跳转链接
   ========================================================================== */
.skip-link {
  position: fixed;
  top: var(--space-2);
  left: var(--space-2);
  z-index: 300;
  transform: translateY(-160%);
  padding: 12px var(--space-3);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-left: 4px solid var(--color-primary);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  text-decoration: none;
  transition: transform 0.18s ease;
}
.skip-link:focus {
  transform: translateY(0);
  color: var(--color-contrast-ink);
}

/* ==========================================================================
   02 · 悬浮胶囊导航（头部）
   ========================================================================== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 80;
  padding: var(--space-2) var(--space-2) 0;
  background-color: transparent;
}

.header-inner {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  max-width: var(--container);
  margin: 0 auto;
  padding: 10px var(--space-3);
  background-color: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-left: 4px solid var(--color-primary);
}

.brand {
  display: inline-flex;
  align-items: baseline;
  gap: var(--space-2);
  min-width: 0;
  text-decoration: none;
  color: var(--color-ink);
}
.brand-index {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.16em;
  color: var(--color-primary);
  white-space: nowrap;
}
.brand-name {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  line-height: 1.1;
  white-space: nowrap;
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: 10px;
  padding: 8px 12px;
  background-color: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  color: var(--color-ink);
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0.06em;
  cursor: pointer;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.nav-toggle-icon {
  position: relative;
  display: block;
  width: 18px;
  height: 2px;
  background-color: currentColor;
}
.nav-toggle-icon::before,
.nav-toggle-icon::after {
  content: "";
  position: absolute;
  left: 0;
  width: 18px;
  height: 2px;
  background-color: currentColor;
}
.nav-toggle-icon::before { top: -6px; }
.nav-toggle-icon::after { top: 6px; }
.nav-toggle[aria-expanded="true"] {
  background-color: var(--color-contrast-surface);
  border-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.nav-toggle-label { line-height: 1; }

.site-nav { display: block; }
.nav-list {
  display: flex;
  align-items: center;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.nav-link {
  display: block;
  padding: 8px var(--space-2);
  border: var(--border-thin) solid transparent;
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  font-weight: 600;
  line-height: 1.3;
  letter-spacing: 0.02em;
  text-decoration: none;
  white-space: nowrap;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.nav-link:hover {
  background-color: var(--color-surface-alt);
  border-color: var(--color-line);
  color: var(--color-ink);
}
.nav-link[aria-current="page"] {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}

/* ==========================================================================
   03 · 容器 / 章节 / 网格
   ========================================================================== */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--space-3);
}

.section {
  padding-block: var(--section-y);
  border-top: var(--border-thin) solid var(--color-line);
}
.section--lg { padding-block: var(--section-y-lg); }
.section--flush { padding-block: 0; border-top: 0; }
.section--dark {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-top-color: var(--color-contrast-line);
}
.section--dark h1,
.section--dark h2,
.section--dark h3,
.section--dark h4 { color: var(--color-contrast-ink); }
.section--dark p { color: color-mix(in srgb, var(--color-contrast-ink) 78%, transparent); }
.section--dark .lede { color: color-mix(in srgb, var(--color-contrast-ink) 82%, transparent); }
.section--dark .eyebrow,
.section--dark .section-index { color: var(--color-contrast-accent); }

.rule {
  height: 1px;
  border: 0;
  background-color: var(--color-line);
}

.grid-12 {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--gutter);
}
.col-3 { grid-column: span 3; }
.col-4 { grid-column: span 4; }
.col-5 { grid-column: span 5; }
.col-6 { grid-column: span 6; }
.col-7 { grid-column: span 7; }
.col-8 { grid-column: span 8; }
.col-9 { grid-column: span 9; }
.col-12 { grid-column: span 12; }

@media (min-width: 961px) {
  .section--offset .container { padding-inline-start: calc(var(--gutter) * 3); }
}

/* ==========================================================================
   04 · 文字标记与编号体系
   ========================================================================== */
.eyebrow {
  display: block;
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-primary);
}

.section-index {
  display: inline-block;
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
}

.display {
  margin: 0;
  font-family: var(--font-heading);
  font-size: var(--text-display);
  font-weight: var(--weight-heading);
  line-height: 0.94;
  letter-spacing: -0.03em;
}

.figure {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  font-weight: 700;
  line-height: 0.9;
  letter-spacing: -0.04em;
}

.lede {
  max-width: var(--measure);
  margin: 0;
  font-size: var(--text-lg);
  line-height: 1.6;
  color: var(--color-ink-soft);
}

.mono {
  font-family: var(--font-mono);
  letter-spacing: 0.06em;
}

.index-tag {
  display: inline-block;
  padding: 3px 7px;
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  line-height: 1.4;
  white-space: nowrap;
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 8px;
  border: var(--border-thin) solid var(--color-line);
  background-color: var(--color-surface-alt);
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  line-height: 1.4;
  white-space: nowrap;
}
.tag--active {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.tag--dark {
  background-color: var(--color-contrast-surface);
  border-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.status-dot {
  display: inline-block;
  flex: none;
  width: 7px;
  height: 7px;
  background-color: var(--color-primary);
}

/* ==========================================================================
   05 · 按钮
   ========================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 12px var(--space-3);
  border: var(--border-thin) solid var(--color-ink);
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-sm);
  font-weight: 600;
  line-height: 1.2;
  letter-spacing: 0.02em;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.btn:hover { background-color: var(--color-surface-alt); }

.btn--primary {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.btn--primary:hover {
  background-color: var(--color-accent);
  border-color: var(--color-accent);
  color: var(--color-accent-ink);
}

.btn--dark {
  background-color: var(--color-contrast-surface);
  border-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.btn--dark:hover {
  background-color: var(--color-contrast-accent);
  border-color: var(--color-contrast-accent);
  color: var(--color-contrast-ink);
}

.btn--ghost {
  background-color: transparent;
  border-color: var(--color-line);
  color: var(--color-ink-soft);
}
.btn--ghost:hover {
  background-color: var(--color-surface-alt);
  color: var(--color-ink);
}

/* ==========================================================================
   06 · 面包屑
   ========================================================================== */
.breadcrumb {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
}
.breadcrumb-list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.breadcrumb-list li {
  display: inline-flex;
  align-items: center;
  gap: 10px;
}
.breadcrumb-list li + li::before {
  content: "/";
  color: var(--color-line);
}
.breadcrumb-list a {
  color: var(--color-ink-soft);
  text-decoration: none;
}
.breadcrumb-list a:hover { color: var(--color-primary); }

/* ==========================================================================
   07 · 正文阅读容器
   ========================================================================== */
.prose {
  max-width: var(--measure);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}
.prose h2 {
  margin: var(--space-6) 0 var(--space-3);
  padding-top: var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
  font-size: var(--text-2xl);
  color: var(--color-ink);
}
.prose h3 {
  margin: var(--space-4) 0 var(--space-2);
  font-size: var(--text-xl);
  color: var(--color-ink);
}
.prose p { margin: 0 0 var(--space-3); }
.prose ul,
.prose ol {
  margin: 0 0 var(--space-3);
  padding-left: var(--space-3);
}
.prose li { margin-bottom: 6px; }
.prose a { color: var(--color-primary); text-underline-offset: 3px; }
.prose strong { color: var(--color-ink); font-weight: 600; }
.prose code {
  padding: 2px 5px;
  background-color: var(--color-surface-alt);
  font-family: var(--font-mono);
  font-size: 0.92em;
  color: var(--color-ink);
}

/* ==========================================================================
   08 · 图片容器（去边直角）
   ========================================================================== */
.media {
  position: relative;
  display: block;
  overflow: hidden;
  background-color: var(--color-surface-deep);
}
.media img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.media--ratio-16-9 { aspect-ratio: 16 / 9; }
.media--ratio-4-3 { aspect-ratio: 4 / 3; }
.media--ratio-1-1 { aspect-ratio: 1 / 1; }
.media--ratio-3-4 { aspect-ratio: 3 / 4; }

.media-frame {
  margin: 0;
  border: var(--border-thin) solid var(--color-line);
  background-color: var(--color-surface);
}
.media-frame .media { border-bottom: var(--border-thin) solid var(--color-line); }
.media-caption {
  padding: 12px var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  line-height: 1.6;
  color: var(--color-ink-muted);
}

.media-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  gap: var(--space-1);
  padding: var(--space-3);
  background: var(--overlay-scrim);
  color: var(--color-contrast-ink);
}

/* ==========================================================================
   09 · 章节目录跟随
   ========================================================================== */
[data-toc-link] {
  display: block;
  padding: 7px 0 7px var(--space-2);
  border-left: 2px solid var(--color-line);
  color: var(--color-ink-muted);
  font-size: var(--text-sm);
  line-height: 1.5;
  text-decoration: none;
  transition: color 0.18s ease, border-color 0.18s ease;
}
[data-toc-link]:hover { color: var(--color-ink); }
[data-toc-link][aria-current] {
  border-left-color: var(--color-primary);
  color: var(--color-primary);
}

/* ==========================================================================
   10 · 长内容淡入
   ========================================================================== */
[data-reveal-state="hidden"] {
  opacity: 0;
  transform: translateY(14px);
}
[data-reveal-state="shown"] {
  opacity: 1;
  transform: none;
  transition: opacity 0.5s ease, transform 0.5s ease;
}

/* ==========================================================================
   11 · 滚动进度与返回顶部
   ========================================================================== */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  z-index: 200;
  background-color: transparent;
  pointer-events: none;
}
.scroll-progress-bar {
  display: block;
  width: 0;
  height: 100%;
  background-color: var(--color-primary);
}

.to-top {
  position: fixed;
  right: var(--space-3);
  bottom: var(--space-3);
  z-index: 120;
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 10px var(--space-2);
  border: var(--border-thin) solid var(--color-contrast-line);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.2s ease, transform 0.2s ease, visibility 0.2s ease, background-color 0.2s ease;
}
.to-top[data-visible="true"] {
  opacity: 1;
  visibility: visible;
  transform: none;
}
.to-top:hover {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.to-top-arrow {
  display: block;
  font-size: var(--text-sm);
  line-height: 1;
}

/* ==========================================================================
   12 · 页脚（大字收尾）
   ========================================================================== */
.site-footer {
  margin-top: var(--section-y);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-top: 1px solid var(--color-contrast-line);
}

.footer-inner {
  max-width: var(--container);
  margin-inline: auto;
  padding: var(--section-y-lg) var(--space-3) var(--space-4);
}

.footer-display {
  display: grid;
  gap: var(--space-2);
  padding-bottom: var(--space-6);
  border-bottom: 1px solid var(--color-contrast-line);
}
.footer-kicker {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--color-contrast-accent);
}
.footer-brand {
  margin: 0;
  font-family: var(--font-heading);
  font-size: var(--text-display);
  font-weight: var(--weight-heading);
  line-height: 0.92;
  letter-spacing: -0.035em;
  color: var(--color-contrast-ink);
  word-break: break-word;
}
.footer-slogan {
  margin: 0;
  padding-left: 4px;
  border-left: 3px solid var(--color-contrast-accent);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.12em;
  color: color-mix(in srgb, var(--color-contrast-ink) 84%, transparent);
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--gutter);
  padding: var(--space-6) 0;
  border-bottom: 1px solid var(--color-contrast-line);
}
.footer-col { min-width: 0; }
.footer-title {
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-contrast-accent);
}
.footer-list {
  display: grid;
  gap: 10px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.footer-list li { line-height: 1.62; }
.footer-list a,
.footer-list span {
  font-size: var(--text-sm);
  color: color-mix(in srgb, var(--color-contrast-ink) 88%, transparent);
  text-decoration: none;
  word-break: break-word;
}
.footer-list a { border-bottom: 1px solid transparent; }
.footer-list a:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}

.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
  padding-top: var(--space-4);
}
.footer-legal {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: color-mix(in srgb, var(--color-contrast-ink) 62%, transparent);
}

/* ==========================================================================
   13 · 响应式
   ========================================================================== */
@media (max-width: 1100px) {
  .nav-link { padding: 8px 12px; }
}

@media (max-width: 1000px) {
  .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 960px) {
  .site-header { padding: var(--space-2) var(--space-2) 0; }

  .nav-toggle { display: inline-flex; }

  .site-nav {
    position: absolute;
    top: calc(100% + 4px);
    left: -1px;
    right: -1px;
    display: none;
    max-height: 72vh;
    overflow-y: auto;
    padding: var(--space-2);
    background-color: var(--color-surface);
    border: var(--border-thin) solid var(--color-line);
    border-top: 3px solid var(--color-primary);
  }
  .site-nav[data-open="true"] { display: block; }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
  }
  .nav-link {
    padding: 13px var(--space-2);
    border: 0;
    border-bottom: var(--border-thin) solid var(--color-line);
    white-space: normal;
  }
  .nav-list li:last-child .nav-link { border-bottom: 0; }
  .nav-link[aria-current="page"] { border-bottom-color: var(--color-primary); }

  .grid-12 { grid-template-columns: repeat(6, minmax(0, 1fr)); }
  .col-3, .col-4, .col-5 { grid-column: span 6; }
  .col-6, .col-7, .col-8, .col-9 { grid-column: span 6; }

  [id] { scroll-margin-top: 96px; }
}

@media (max-width: 720px) {
  .section { padding-block: var(--space-8); }
  .section--lg { padding-block: var(--space-8); }
  .footer-inner { padding-top: var(--space-8); }
  .footer-grid { grid-template-columns: 1fr; gap: var(--space-4); }
  .grid-12 { grid-template-columns: 1fr; }
  .col-3, .col-4, .col-5, .col-6, .col-7, .col-8, .col-9, .col-12 { grid-column: span 1; }
  .lede { font-size: var(--text-base); }
}

@media (max-width: 520px) {
  .header-inner { padding: 8px var(--space-2); gap: var(--space-2); }
  .brand-name { font-size: var(--text-base); }
  .nav-toggle-label { display: none; }
  .site-footer { margin-top: var(--space-8); }
  .to-top { right: var(--space-2); bottom: var(--space-2); }
  .to-top-label { display: none; }
  .to-top { padding: 12px; }
}

/* ==========================================================================
   14 · 无障碍与减少动态
   ========================================================================== */
@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;
    scroll-behavior: auto !important;
  }
  [data-reveal-state="hidden"] { opacity: 1; transform: none; }
}