*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { -webkit-text-size-adjust: 100%; background: var(--background); }
body {
  background: var(--background);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.75;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
img, svg, video { display: block; max-width: 100%; height: auto; }
a { color: var(--primary); text-underline-offset: 3px; }
button { font: inherit; cursor: pointer; }
ul[class], ol[class] { list-style: none; margin: 0; padding: 0; }
::selection { background: var(--primary); color: #fff; }
h1, h2, h3, h4 { font-family: var(--font-display); line-height: 1.25; color: var(--text); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }

:root {
  --primary: #E60012;
  --primary-dark: #9E0000;
  --background: #0D0D0D;
  --surface: #1A1A1A;
  --surface-raised: #262626;
  --text: #F2F2F2;
  --muted: #A0A0A0;
  --accent: #D4AF37;
  --accent-soft: rgba(212, 175, 55, 0.2);
  --primary-soft: rgba(230, 0, 18, 0.15);
  --sidebar-w: 300px;
  --header-h: 64px;
  --font-display: "Inter", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-body: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --ease-out: cubic-bezier(0.22, 1, 0.36, 1);
}

@media (min-width: 769px) {
  #main-content { margin-left: var(--sidebar-w); }
  .site-footer { margin-left: var(--sidebar-w); }
}
@media (min-width: 769px) and (max-width: 1024px) {
  :root { --sidebar-w: 260px; }
  .l-container { padding-inline: 32px; }
}

#main-content { min-height: 70vh; }
.l-container {
  width: 100%;
  max-width: 1180px;
  margin-inline: auto;
  padding-inline: 48px;
}
.section-block { margin: 0 0 72px; }
.section-block:last-child { margin-bottom: 0; }

.skip-link {
  position: fixed;
  top: -64px;
  left: 16px;
  z-index: 1000;
  background: var(--primary);
  color: #fff;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.875rem;
  padding: 10px 16px;
  text-decoration: none;
  clip-path: polygon(0 0, calc(100% - 10px) 0, 100% 10px, 100% 100%, 0 100%);
  transition: top 180ms var(--ease-out);
}
.skip-link:focus { top: 12px; }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 13px 22px;
  font-family: var(--font-body);
  font-weight: 700;
  font-size: 0.9375rem;
  line-height: 1;
  text-decoration: none;
  color: var(--text);
  background: var(--surface-raised);
  border: 2px solid transparent;
  cursor: pointer;
  -webkit-appearance: none;
  appearance: none;
  clip-path: polygon(0 0, calc(100% - 12px) 0, 100% 12px, 100% 100%, 0 100%);
  transition: background 160ms ease, color 160ms ease, border-color 160ms ease, transform 160ms var(--ease-out), box-shadow 160ms ease;
}
.btn--primary {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}
.btn--primary:hover {
  background: var(--primary-dark);
  border-color: var(--primary-dark);
  transform: translateX(2px);
  box-shadow: 4px 4px 0 var(--primary-soft);
}
.btn--ghost {
  background: transparent;
  border-color: rgba(255, 255, 255, 0.22);
  color: var(--text);
}
.btn--ghost:hover {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent);
}
.btn--block { display: flex; width: 100%; }

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: var(--text);
  text-decoration: none;
}
.brand__badge {
  position: relative;
  display: grid;
  place-items: center;
  width: 46px;
  height: 46px;
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: #fff;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 1.35rem;
  line-height: 1;
  border: 1px solid rgba(212, 175, 55, 0.45);
  clip-path: polygon(0 0, calc(100% - 10px) 0, 100% 10px, 100% 100%, 0 100%);
  transition: transform 180ms var(--ease-out);
}
.brand:hover .brand__badge { transform: rotate(-5deg) scale(1.04); }
.brand__copy { display: flex; flex-direction: column; gap: 2px; }
.brand__name {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 1.125rem;
  letter-spacing: 0.06em;
  line-height: 1.2;
}
.brand__tag {
  font-size: 0.72rem;
  color: var(--muted);
  letter-spacing: 0.14em;
  line-height: 1.2;
}

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  width: var(--sidebar-w);
  z-index: 100;
  display: flex;
  flex-direction: column;
  padding: 32px 24px 24px;
  background:
    repeating-linear-gradient(-45deg, transparent 0 12px, rgba(255, 255, 255, 0.018) 12px 14px),
    var(--surface);
  border-right: 2px solid var(--primary);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 24px), calc(100% - 24px) 100%, 0 100%);
}
.site-header__bar {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.site-header__bar::after {
  content: "";
  display: block;
  width: 100%;
  height: 2px;
  margin-top: 12px;
  background: linear-gradient(90deg, var(--primary) 0 45%, var(--accent) 45% 55%, transparent 55%);
}
.site-header__panel {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 20px;
  position: relative;
  margin-top: 28px;
  padding-top: 24px;
  border-top: 1px solid rgba(255, 255, 255, 0.07);
}
.site-header__panel::before {
  content: "";
  position: absolute;
  top: -1px;
  left: 0;
  width: 72px;
  height: 2px;
  background: var(--primary);
}
.site-header__cta { margin-top: auto; }

.site-nav { display: block; }
.site-nav__list { display: flex; flex-direction: column; gap: 2px; }
.site-nav__link {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 12px;
  color: var(--muted);
  text-decoration: none;
  font-size: 0.9375rem;
  font-weight: 500;
  border-left: 2px solid transparent;
  transition: background 160ms ease, color 160ms ease, border-color 160ms ease;
}
.site-nav__link::before {
  content: "";
  width: 6px;
  height: 6px;
  flex-shrink: 0;
  background: currentColor;
  transform: rotate(45deg);
  transition: background 160ms ease;
}
.site-nav__link:hover {
  color: var(--text);
  background: var(--primary-soft);
  border-left-color: var(--primary);
}
.site-nav__link[aria-current="page"] {
  color: #fff;
  background: linear-gradient(90deg, var(--primary-soft), transparent 90%);
  border-left-color: var(--primary);
  font-weight: 700;
}
.site-nav__link[aria-current="page"]::before { background: var(--primary); }

.nav-toggle { display: none; }

.site-footer {
  background: var(--surface);
  border-top: 3px solid var(--primary);
  padding: 56px clamp(20px, 4vw, 48px) 28px;
  position: relative;
}
.site-footer::before {
  content: "";
  position: absolute;
  top: -3px;
  left: 0;
  width: 180px;
  height: 3px;
  background: linear-gradient(90deg, var(--accent), transparent 90%);
}
.site-footer__grid {
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr;
  gap: 40px;
  max-width: 1120px;
}
.site-footer__col { min-width: 0; }
.site-footer__col--brand {
  position: relative;
  padding-left: 18px;
}
.site-footer__col--brand::before {
  content: "";
  position: absolute;
  left: 0;
  top: 2px;
  bottom: 2px;
  width: 3px;
  background: linear-gradient(180deg, var(--primary) 0 60%, var(--accent) 60% 100%);
}
.site-footer__trust {
  margin-top: 16px;
  color: var(--muted);
  font-size: 0.875rem;
  line-height: 1.7;
}
.site-footer__trust::before {
  content: "";
  display: inline-block;
  width: 6px;
  height: 6px;
  margin-right: 8px;
  background: var(--accent);
  transform: rotate(45deg);
  vertical-align: middle;
}
.site-footer__contact {
  margin-top: 14px;
  color: var(--muted);
  font-size: 0.8125rem;
  line-height: 1.9;
}
.site-footer__heading {
  margin-bottom: 14px;
  font-family: var(--font-display);
  font-size: 0.8125rem;
  font-weight: 800;
  letter-spacing: 0.16em;
  color: var(--accent);
  text-transform: uppercase;
}
.site-footer__heading::after {
  content: "";
  display: block;
  width: 28px;
  height: 2px;
  margin-top: 8px;
  background: var(--primary);
}
.site-footer__list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.site-footer__list a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.875rem;
  transition: color 160ms ease, padding-left 160ms ease;
}
.site-footer__list a:hover {
  color: var(--text);
  padding-left: 5px;
}
.site-footer__list a[aria-current="page"] { color: var(--accent); }
.site-footer__bottom {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 12px;
  margin-top: 44px;
  padding-top: 20px;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  color: var(--muted);
  font-size: 0.8125rem;
}
.site-footer__icp { letter-spacing: 0.02em; }

.back-to-top {
  position: fixed;
  right: 20px;
  bottom: 24px;
  z-index: 96;
  width: 52px;
  height: 52px;
  display: grid;
  place-items: center;
  color: var(--text);
  background: var(--surface-raised);
  border: 1px solid rgba(230, 0, 18, 0.55);
  cursor: pointer;
  clip-path: polygon(0 0, calc(100% - 12px) 0, 100% 12px, 100% 100%, 0 100%);
  opacity: 0;
  visibility: hidden;
  transform: translateY(14px);
  transition: opacity 180ms ease, transform 180ms ease, visibility 180ms ease, border-color 180ms ease;
}
.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.back-to-top::before {
  content: "";
  position: absolute;
  inset: 4px;
  border-radius: 50%;
  background: conic-gradient(var(--primary) calc(var(--scroll-progress, 0) * 1turn), rgba(255, 255, 255, 0.1) 0);
  z-index: 0;
  pointer-events: none;
}
.back-to-top:hover { border-color: var(--accent); }
.back-to-top__icon {
  position: relative;
  z-index: 1;
  font-family: var(--font-display);
  font-size: 1.4rem;
  font-weight: 900;
  line-height: 1;
  transform: translateY(-1px);
  transition: color 180ms ease;
}
.back-to-top:hover .back-to-top__icon { color: var(--accent); }

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin-bottom: 28px;
  font-size: 0.8125rem;
  color: var(--muted);
}
.breadcrumb li { display: flex; align-items: center; }
.breadcrumb li + li::before {
  content: "/";
  margin-right: 8px;
  color: var(--primary);
  font-weight: 700;
}
.breadcrumb a { color: var(--muted); text-decoration: none; }
.breadcrumb a:hover { color: var(--text); }
.breadcrumb [aria-current="page"] { color: var(--accent); }

.section-label {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--accent);
  font-size: 0.8125rem;
  font-weight: 800;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}
.section-label::before {
  content: "";
  width: 24px;
  height: 2px;
  background: var(--primary);
}
.section-number {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(3rem, 6vw, 5.5rem);
  line-height: 0.9;
  color: transparent;
  -webkit-text-stroke: 1.5px var(--primary);
  letter-spacing: 0.02em;
  margin: 0;
}

.toc-list { counter-reset: toc; }
.toc-list li { counter-increment: toc; border-bottom: 1px solid rgba(255, 255, 255, 0.07); }
.toc-list a {
  display: flex;
  align-items: baseline;
  gap: 16px;
  padding: 13px 4px;
  color: var(--muted);
  text-decoration: none;
  transition: color 160ms ease, padding-left 160ms ease, background 160ms ease;
}
.toc-list a::before {
  content: counter(toc, decimal-leading-zero);
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 0.75rem;
  color: var(--primary);
}
.toc-list a:hover {
  color: var(--text);
  padding-left: 8px;
  background: linear-gradient(90deg, var(--primary-soft), transparent);
}

.chip-panel {
  position: relative;
  background: var(--surface);
  padding: 28px;
  clip-path: polygon(0 0, calc(100% - 16px) 0, 100% 16px, 100% 100%, 16px 100%, 0 calc(100% - 16px));
}
.chip-panel--accent { border-left: 3px solid var(--accent); }

.stat-card {
  background: var(--surface);
  padding: 20px 20px 18px;
  border-top: 3px solid var(--primary);
  clip-path: polygon(0 0, calc(100% - 14px) 0, 100% 14px, 100% 100%, 0 100%);
}
.stat-card__label {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  color: var(--muted);
  text-transform: uppercase;
}
.stat-card__value {
  display: block;
  margin-top: 6px;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 2.25rem;
  line-height: 1;
  color: var(--text);
}
.stat-card__value--gold { color: var(--accent); }

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 12px;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--muted);
  background: rgba(255, 255, 255, 0.04);
  border-left: 2px solid var(--primary);
}
.tag::before {
  content: "";
  width: 4px;
  height: 4px;
  background: currentColor;
  transform: rotate(45deg);
}
.tag--gold {
  color: var(--accent);
  background: var(--accent-soft);
  border-left-color: var(--accent);
}

.image-frame {
  position: relative;
  display: block;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background:
    repeating-linear-gradient(-45deg, rgba(255, 255, 255, 0.025) 0 2px, transparent 2px 8px),
    var(--surface);
  clip-path: polygon(0 0, calc(100% - 20px) 0, 100% 20px, 100% 100%, 0 100%);
}
.image-frame::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, var(--primary-soft), transparent 60%);
}
.image-frame--tall { aspect-ratio: 3 / 4; }
.image-frame--wide { aspect-ratio: 21 / 9; }

.speed-line {
  position: relative;
  display: block;
  height: 2px;
  background: linear-gradient(90deg, var(--primary), transparent 85%);
}
.speed-line::after {
  content: "";
  position: absolute;
  right: 0;
  top: 50%;
  width: 7px;
  height: 7px;
  background: var(--accent);
  transform: translateY(-50%) rotate(45deg);
}
.speed-line--reverse { background: linear-gradient(270deg, var(--primary), transparent 85%); }
.speed-line--reverse::after {
  right: auto;
  left: 0;
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}
.grid { display: grid; gap: 24px; }
.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }

.accordion { border-top: 1px solid rgba(255, 255, 255, 0.08); }
.accordion__item { border-bottom: 1px solid rgba(255, 255, 255, 0.08); }
.accordion__heading { margin: 0; }
.accordion__trigger {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 18px 4px;
  background: transparent;
  border: none;
  cursor: pointer;
  color: var(--text);
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1rem;
  text-align: left;
  line-height: 1.4;
  transition: color 160ms ease;
}
.accordion__trigger:hover { color: var(--accent); }
.accordion__trigger::after {
  content: "+";
  display: inline-block;
  flex-shrink: 0;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 1.4rem;
  line-height: 1;
  color: var(--primary);
  transition: transform 200ms var(--ease-out), color 160ms ease;
}
.accordion__item[data-open] .accordion__trigger { color: var(--accent); }
.accordion__item[data-open] .accordion__trigger::after {
  transform: rotate(45deg);
  color: var(--accent);
}
.accordion__panel {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 240ms var(--ease-out);
}
.accordion__item[data-open] .accordion__panel { grid-template-rows: 1fr; }
.accordion__content {
  overflow: hidden;
  min-height: 0;
  padding-right: 40px;
  color: var(--muted);
  font-size: 0.9375rem;
  line-height: 1.8;
}
.accordion__content > * + * { margin-top: 12px; }

.js [data-reveal] {
  opacity: 0;
  transform: translateY(22px);
  transition: opacity 500ms var(--ease-out), transform 500ms var(--ease-out);
  transition-delay: var(--reveal-delay, 0ms);
}
.js [data-reveal].is-revealed {
  opacity: 1;
  transform: none;
}

@media (max-width: 768px) {
  .l-container { padding-inline: 20px; }
  #main-content { padding-top: var(--header-h); }

  .site-header {
    top: 0;
    left: 0;
    right: 0;
    bottom: auto;
    width: auto;
    height: var(--header-h);
    flex-direction: row;
    align-items: center;
    padding: 0 14px;
    background: var(--surface);
    border-right: none;
    border-bottom: 2px solid var(--primary);
    clip-path: none;
  }
  .site-header__bar {
    width: 100%;
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
  }
  .site-header__bar::after { display: none; }
  .brand__badge { width: 36px; height: 36px; font-size: 1.1rem; }
  .brand__tag { display: none; }

  .site-header__panel {
    position: fixed;
    top: var(--header-h);
    left: 0;
    bottom: 0;
    width: min(300px, 84vw);
    margin-top: 0;
    padding: 28px 20px 32px;
    border-top: none;
    border-right: 2px solid var(--primary);
    background: var(--surface);
    transform: translateX(-100%);
    visibility: hidden;
    transition: transform 220ms var(--ease-out), box-shadow 220ms var(--ease-out), visibility 0s 220ms;
    overflow-y: auto;
    z-index: 98;
  }
  .site-header__panel[data-open] {
    transform: translateX(0);
    visibility: visible;
    box-shadow: 16px 0 40px rgba(0, 0, 0, 0.5);
    transition: transform 220ms var(--ease-out), box-shadow 220ms var(--ease-out), visibility 0s;
  }

  .nav-toggle {
    display: inline-flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 5px;
    width: 44px;
    height: 44px;
    padding: 0;
    color: var(--text);
  }
  .nav-toggle__line {
    display: block;
    width: 18px;
    height: 2px;
    background: currentColor;
    transition: transform 180ms ease, opacity 180ms ease;
  }
  .nav-toggle[aria-expanded="true"] .nav-toggle__line:nth-child(1) { transform: translateY(7px) rotate(45deg); }
  .nav-toggle[aria-expanded="true"] .nav-toggle__line:nth-child(2) { opacity: 0; }
  .nav-toggle[aria-expanded="true"] .nav-toggle__line:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

  body:has(.site-header__panel[data-open])::before {
    content: "";
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.55);
    z-index: 97;
  }

  .site-footer { padding: 40px 20px 24px; }
  .site-footer__grid { grid-template-columns: 1fr; gap: 32px; }
  .site-footer__bottom { flex-direction: column; align-items: flex-start; }

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

@media (max-width: 1024px) and (min-width: 769px) {
  .site-footer__grid { grid-template-columns: 1fr 1fr; }
  .site-footer__col--brand { grid-column: 1 / -1; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
  .js [data-reveal] {
    opacity: 1;
    transform: none;
    transition: none;
  }
}

::-webkit-scrollbar { width: 10px; height: 10px; background: var(--background); }
::-webkit-scrollbar-thumb { background: var(--primary-dark); border: 2px solid var(--background); }
::-webkit-scrollbar-thumb:hover { background: var(--primary); }