:root {
  --color-surface: #fbfbfb;
  --color-surface-alt: #f1f1f1;
  --color-surface-deep: #e3e3e3;
  --color-ink: #363130;
  --color-ink-soft: #665e5c;
  --color-ink-muted: #827a78;
  --color-line: #d8d7d6;
  --color-primary: #d93a12;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #f6e0da;
  --color-accent: #1878ce;
  --color-accent-ink: #ffffff;
  --color-highlight: #d2e3f3;
  --color-focus: #0c71cb;
  --color-contrast-surface: #2e1a15;
  --color-contrast-ink: #e7e5e4;
  --color-contrast-line: #574743;
  --color-contrast-accent: #248be6;
  --overlay-scrim: linear-gradient(180deg, rgba(46, 26, 21, 0.35) 0%, rgba(46, 26, 21, 0.72) 55%, rgba(46, 26, 21, 0.92) 100%);
  --font-heading: "Source Han Sans SC", "Noto Sans SC", SimHei, "Microsoft YaHei", sans-serif;
  --font-body: "PingFang SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 10.1px;
  --text-sm: 14.3px;
  --text-base: 17px;
  --text-lg: 24.0px;
  --text-xl: 34.0px;
  --text-2xl: 48.1px;
  --text-3xl: 68.0px;
  --text-4xl: 96.1px;
  --text-display: clamp(49px, 10.0vw, 128px);
  --text-figure: clamp(40px, 7.2vw, 92px);
  --weight-heading: 780;
  --weight-body: 400;
  --leading-body: 1.77;
  --leading-heading: 1.17;
  --tracking-heading: -0.019em;
  --radius-sm: 1px;
  --radius-md: 1px;
  --radius-lg: 1px;
  --radius-pill: 1px;
  --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: 1180px;
  --measure: 72ch;
  --gutter: 24px;
  --section-y: 96px;
  --section-y-lg: 134px;
}

/* ============================================================
   1. 归零
   ============================================================ */
*,
*::before,
*::after { box-sizing: border-box; }

html {
  -webkit-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);
  overflow-wrap: break-word;
  -webkit-font-smoothing: antialiased;
}

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

p { margin: 0; }

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

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

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

button {
  font: inherit;
  color: inherit;
  background: none;
  border: 0;
}

[hidden] { display: none !important; }

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

.skip-link {
  position: absolute;
  left: var(--space-3);
  top: -120px;
  z-index: 200;
  padding: 10px 18px;
  background: var(--color-accent);
  color: var(--color-accent-ink);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: 700;
  border-radius: var(--radius-sm);
  transition: top 150ms linear;
}
.skip-link:focus { top: var(--space-2); }

/* ============================================================
   2. 布局骨架 / 色块反转分区
   ============================================================ */
.shell {
  width: min(100% - var(--space-6), var(--container));
  margin-inline: auto;
}

.band {
  padding-block: var(--section-y);
  background: var(--color-surface);
  color: var(--color-ink);
}
.band--lg { padding-block: var(--section-y-lg); }
.band--tight { padding-block: var(--space-6); }

.band--surface { background: var(--color-surface); color: var(--color-ink); }
.band--surface-alt { background: var(--color-surface-alt); color: var(--color-ink); }
.band--primary { background: var(--color-primary); color: var(--color-primary-ink); }
.band--accent { background: var(--color-accent); color: var(--color-accent-ink); }
.band--deep { background: var(--color-contrast-surface); color: var(--color-contrast-ink); }

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

/* ============================================================
   3. 标题 / 文字组件
   ============================================================ */
.section-head {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  margin-bottom: var(--space-6);
}

.eyebrow {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.eyebrow__num {
  font-size: var(--text-lg);
  font-weight: 700;
  letter-spacing: 0.02em;
  font-variant-numeric: tabular-nums;
}
.eyebrow__text { font-size: var(--text-sm); }

.band--primary .eyebrow,
.band--accent .eyebrow,
.band--deep .eyebrow {
  color: inherit;
  opacity: 0.76;
}

.section-title {
  font-size: var(--text-xl);
  max-width: 30ch;
}

.lede {
  max-width: var(--measure);
  font-size: var(--text-lg);
  line-height: 1.5;
  color: var(--color-ink-soft);
}
.band--primary .lede,
.band--accent .lede,
.band--deep .lede {
  color: inherit;
  opacity: 0.84;
}

.prose {
  max-width: var(--measure);
  font-size: var(--text-base);
}
.prose > * + * { margin-top: var(--space-3); }
.prose h2 {
  font-size: var(--text-xl);
  margin-top: var(--space-6);
}
.prose h3 {
  font-size: var(--text-lg);
  margin-top: var(--space-4);
}
.prose ul,
.prose ol {
  padding-left: 1.45em;
  list-style: disc;
}
.prose ol { list-style: decimal; }
.prose li + li { margin-top: var(--space-1); }
.prose a {
  color: var(--color-accent);
  border-bottom: var(--border-thin) solid currentColor;
}
.band--primary .prose a,
.band--accent .prose a,
.band--deep .prose a {
  color: inherit;
  border-bottom-color: currentColor;
}

.stat {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}
.stat__value {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  font-weight: 700;
  line-height: 0.94;
  letter-spacing: -0.04em;
  font-variant-numeric: tabular-nums;
}
.stat__label {
  font-size: var(--text-sm);
  line-height: 1.5;
  color: var(--color-ink-muted);
}
.band--primary .stat__label,
.band--accent .stat__label,
.band--deep .stat__label {
  color: inherit;
  opacity: 0.78;
}

/* ============================================================
   4. 通用组件
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 12px 22px;
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: 700;
  line-height: 1.2;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background-color 150ms linear, color 150ms linear, border-color 150ms linear;
}
.btn--primary {
  background: var(--color-primary);
  color: var(--color-primary-ink);
}
.btn--primary:hover {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.btn--accent {
  background: var(--color-accent);
  color: var(--color-accent-ink);
}
.btn--accent:hover {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.btn--outline {
  background: transparent;
  color: inherit;
  border-color: currentColor;
}
.btn--outline:hover {
  background: var(--color-primary);
  color: var(--color-primary-ink);
  border-color: var(--color-primary);
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 2px 9px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.08em;
  line-height: 1.6;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-sm);
}
.badge--primary {
  background: var(--color-primary);
  color: var(--color-primary-ink);
}
.badge--accent {
  background: var(--color-accent);
  color: var(--color-accent-ink);
}
.badge--outline {
  background: transparent;
  color: inherit;
  border-color: currentColor;
}

.frame {
  padding: var(--space-3);
  background: var(--color-surface-alt);
  color: var(--color-ink);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
}
.frame--flush { padding: 0; }
.band--primary .frame {
  background: color-mix(in srgb, var(--color-primary-ink) 12%, var(--color-primary));
  border-color: color-mix(in srgb, var(--color-primary-ink) 32%, var(--color-primary));
  color: var(--color-primary-ink);
}
.band--accent .frame {
  background: color-mix(in srgb, var(--color-accent-ink) 12%, var(--color-accent));
  border-color: color-mix(in srgb, var(--color-accent-ink) 32%, var(--color-accent));
  color: var(--color-accent-ink);
}
.band--deep .frame {
  background: color-mix(in srgb, var(--color-contrast-ink) 6%, var(--color-contrast-surface));
  border-color: var(--color-contrast-line);
  color: var(--color-contrast-ink);
}

.media {
  position: relative;
  display: block;
  overflow: hidden;
  aspect-ratio: 16 / 10;
  background: var(--color-surface-deep);
  border-radius: var(--radius-sm);
}
.media--wide { aspect-ratio: 21 / 9; }
.media--square { aspect-ratio: 1 / 1; }
.media--tall { aspect-ratio: 3 / 4; }
.media > img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: brightness(0.86) contrast(1.06) saturate(0.92);
}
.media__scrim {
  position: absolute;
  inset: 0;
  background: var(--overlay-scrim);
  pointer-events: none;
}
.media__caption {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 1;
  padding: var(--space-3);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  line-height: 1.5;
}

.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1);
  padding-block: var(--space-2);
}
.filter-chip {
  padding: 7px 15px;
  font-size: var(--text-sm);
  font-weight: 600;
  line-height: 1.2;
  color: inherit;
  background: transparent;
  border: var(--border-thin) solid color-mix(in srgb, currentColor 34%, transparent);
  border-radius: var(--radius-pill);
  cursor: pointer;
  transition: background-color 150ms linear, color 150ms linear, border-color 150ms linear;
}
.filter-chip:hover {
  background: var(--color-primary);
  color: var(--color-primary-ink);
  border-color: var(--color-primary);
}
.filter-chip[aria-pressed="true"] {
  background: var(--color-accent);
  color: var(--color-accent-ink);
  border-color: var(--color-accent);
}

.fold {
  border-top: var(--border-thin) solid color-mix(in srgb, currentColor 22%, transparent);
}
.fold__head {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  width: 100%;
  padding: var(--space-3) 0;
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  text-align: left;
  color: inherit;
  cursor: pointer;
}
.fold__head::after {
  content: "";
  flex: 0 0 auto;
  width: 10px;
  height: 10px;
  margin-left: auto;
  border-right: var(--border-thin) solid currentColor;
  border-bottom: var(--border-thin) solid currentColor;
  transform: rotate(45deg);
  transition: transform 150ms linear;
}
.fold[data-open="true"] .fold__head::after { transform: rotate(-135deg); }
.fold__body { padding-bottom: var(--space-4); }
.fold[data-open="false"] .fold__body { display: none; }

.breadcrumb {
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}
.breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1);
}
.breadcrumb li + li::before {
  content: "/";
  margin-right: var(--space-1);
  opacity: 0.6;
}
.breadcrumb a {
  border-bottom: var(--border-thin) solid transparent;
  transition: border-color 150ms linear;
}
.breadcrumb a:hover { border-bottom-color: currentColor; }
.band--primary .breadcrumb,
.band--accent .breadcrumb,
.band--deep .breadcrumb {
  color: inherit;
  opacity: 0.78;
}

/* ============================================================
   5. 头部
   ============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 90;
  background: var(--color-surface);
}

.header-top {
  background: var(--color-primary);
  color: var(--color-primary-ink);
}
.header-top__inner {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-1) var(--space-3);
  min-height: 38px;
  padding-block: 7px;
}
.brand-line {
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: 700;
  letter-spacing: 0.01em;
}
.brand-since {
  padding: 1px 8px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  line-height: 1.7;
  border: var(--border-thin) solid currentColor;
  border-radius: var(--radius-pill);
  opacity: 0.9;
}
.code-entry {
  display: inline-flex;
  flex-direction: column;
  gap: 0;
  margin-left: auto;
  padding: 4px 12px;
  background: var(--color-primary-ink);
  color: var(--color-primary);
  border-radius: var(--radius-sm);
  transition: background-color 150ms linear, color 150ms linear;
}
.code-entry__label {
  font-size: var(--text-sm);
  font-weight: 700;
  line-height: 1.35;
}
.code-entry__hint {
  font-size: var(--text-xs);
  line-height: 1.35;
  opacity: 0.78;
}
.code-entry:hover,
.code-entry:focus-visible {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.header-main {
  background: var(--color-surface);
  color: var(--color-ink);
}
.header-main__inner {
  display: flex;
  align-items: center;
  gap: var(--space-2) var(--space-3);
  min-height: 66px;
  padding-block: var(--space-2);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  flex: 0 0 auto;
}
.brand__mark {
  display: inline-grid;
  place-items: center;
  width: 36px;
  height: 36px;
  background: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-heading);
  font-size: var(--text-xs);
  font-weight: 700;
  line-height: 1.05;
  letter-spacing: 0.06em;
  border-radius: var(--radius-sm);
  transition: background-color 150ms linear;
}
.brand:hover .brand__mark { background: var(--color-accent); }
.brand__name {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  line-height: 1.1;
  letter-spacing: var(--tracking-heading);
  white-space: nowrap;
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-1);
  margin-left: auto;
  padding: 9px 13px;
  background: var(--color-surface-alt);
  color: var(--color-ink);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  font-weight: 700;
  cursor: pointer;
  position: relative;
  z-index: 2;
}
.nav-toggle__bars {
  display: inline-flex;
  flex-direction: column;
  gap: 3px;
}
.nav-toggle__bars i {
  display: block;
  width: 16px;
  height: 2px;
  background: currentColor;
}
.nav-toggle[aria-expanded="true"] {
  background: var(--color-primary);
  color: var(--color-primary-ink);
  border-color: var(--color-primary);
}

.site-nav { margin-left: auto; }
.site-nav__list {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}
.site-nav__list a {
  display: inline-flex;
  align-items: center;
  padding: 9px 13px;
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: 700;
  line-height: 1.2;
  color: var(--color-ink-soft);
  border-radius: var(--radius-sm);
  transition: background-color 150ms linear, color 150ms linear;
}
.site-nav__list a::before {
  content: "";
  flex: 0 0 auto;
  width: 6px;
  height: 6px;
  margin-right: 8px;
  border: var(--border-thin) solid currentColor;
  border-radius: 50%;
  transition: background-color 150ms linear;
}
.site-nav__list a:hover {
  background: var(--color-primary);
  color: var(--color-primary-ink);
}
.site-nav__list a:hover::before { background: var(--color-primary-ink); }
.site-nav__list a[aria-current="page"] {
  background: var(--color-accent);
  color: var(--color-accent-ink);
}
.site-nav__list a[aria-current="page"]::before { background: var(--color-accent-ink); }

.header-cta {
  display: inline-flex;
  align-items: center;
  flex: 0 0 auto;
  padding: 11px 18px;
  background: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: 700;
  line-height: 1.2;
  border-radius: var(--radius-sm);
  transition: background-color 150ms linear, color 150ms linear;
}
.header-cta:hover {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

/* 宽屏：左侧缓慢自转的悬浮环 */
@media (min-width: 1280px) {
  .site-nav::before {
    content: "";
    position: fixed;
    left: 18px;
    top: 50%;
    width: 28px;
    height: 28px;
    margin-top: -14px;
    border: var(--border-thin) solid var(--color-line);
    border-top-color: var(--color-primary);
    border-right-color: var(--color-accent);
    border-radius: 50%;
    animation: ring-spin 28s linear infinite;
    pointer-events: none;
  }
}
@keyframes ring-spin {
  to { transform: rotate(360deg); }
}

/* ============================================================
   6. 页脚
   ============================================================ */
.site-footer {
  padding-block: var(--space-4);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-top: var(--border-thin) solid var(--color-contrast-line);
}
.site-footer__inner {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-4);
}
.site-footer__line {
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  font-weight: 700;
  line-height: 1.5;
}
.site-footer__links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1) var(--space-3);
  font-size: var(--text-sm);
}
.site-footer__links a {
  padding-bottom: 2px;
  border-bottom: var(--border-thin) solid transparent;
  transition: color 150ms linear, border-color 150ms linear;
}
.site-footer__links a:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}
.site-footer__contact {
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.02em;
  line-height: 1.7;
  opacity: 0.72;
}

/* ============================================================
   7. 动效与脚本钩子
   ============================================================ */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  z-index: 95;
  background: var(--color-accent);
  transform: scaleX(0);
  transform-origin: 0 50%;
  pointer-events: none;
}

.js-on [data-reveal] {
  opacity: 0;
  transform: translate3d(-24px, 0, 0);
  transition: opacity 220ms linear, transform 220ms cubic-bezier(0.2, 0.6, 0.2, 1);
}
.js-on [data-reveal].is-in {
  opacity: 1;
  transform: translate3d(0, 0, 0);
}

/* ============================================================
   8. 断点
   ============================================================ */
@media (max-width: 1023px) {
  .header-cta { display: none; }
  .nav-toggle { display: inline-flex; }

  .site-nav {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    z-index: 80;
    width: min(86vw, 360px);
    margin-left: 0;
    padding: 122px var(--space-3) var(--space-4);
    background: var(--color-contrast-surface);
    color: var(--color-contrast-ink);
    overflow-y: auto;
    transform: translateX(102%);
    visibility: hidden;
    transition: transform 220ms ease, visibility 0s linear 220ms;
  }
  .site-nav[data-open="true"] {
    transform: translateX(0);
    visibility: visible;
    transition: transform 220ms ease, visibility 0s linear 0s;
  }
  .site-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
  }
  .site-nav__list a {
    padding: 15px 4px;
    font-size: var(--text-lg);
    color: var(--color-contrast-ink);
    border-bottom: var(--border-thin) solid var(--color-contrast-line);
    border-radius: 0;
  }
  .site-nav__list a:hover {
    background: var(--color-primary);
    color: var(--color-primary-ink);
  }
  .site-nav__list a[aria-current="page"] {
    background: var(--color-accent);
    color: var(--color-accent-ink);
  }
}

@media (max-width: 899px) {
  .code-entry__hint { display: none; }
  .grid--8 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
  .grid--4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid--3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 720px) {
  .band,
  .band--lg { padding-block: var(--space-8); }
  .section-title { font-size: var(--text-lg); }
  .lede { font-size: var(--text-base); }
}

@media (max-width: 639px) {
  .shell { width: min(100% - var(--space-4), var(--container)); }
  .brand-line { font-size: var(--text-xs); }
  .brand__name { font-size: var(--text-base); }
  .brand__mark { width: 30px; height: 30px; }
  .grid--8,
  .grid--4,
  .grid--3,
  .grid--2 { grid-template-columns: minmax(0, 1fr); }
  .site-footer__contact { margin-left: 0; }
  .site-footer__inner { align-items: flex-start; flex-direction: column; }
}

/* ============================================================
   9. 动效退让
   ============================================================ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

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

  .site-nav::before { display: none; }
  .js-on [data-reveal] { opacity: 1; transform: none; }
}