:root {
  --color-space: #0A1E3C;
  --color-space-deep: #16335B;
  --color-cream: #F5F0E6;
  --color-ink: #2B211C;
  --color-red: #C9372E;
  --color-metal: #8A93A5;
  --color-info: #D9E3EF;
  --color-orange: #E4652F;
  --font-heading: "DIN Alternate", "Bahnschrift", "Noto Sans SC", sans-serif;
  --font-body: "Noto Sans SC", "Microsoft YaHei", sans-serif;
  --font-mono: "JetBrains Mono", "SF Mono", "Menlo", monospace;
  --content-width: 1200px;
  --gutter: 24px;
  --header-z: 100;
  --nav-z: 105;
  --motion-ease: cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

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

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

body {
  margin: 0;
  min-height: 100vh;
  background: var(--color-cream);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: 16px;
  font-weight: 300;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4, h5, h6, p, figure, blockquote, dl, dd {
  margin: 0 0 1em;
}

ul, ol {
  margin: 0 0 1em;
  padding-left: 1.25em;
}

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

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

a {
  color: var(--color-red);
  text-decoration: underline;
  text-underline-offset: 3px;
  transition: color 0.2s ease;
}

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

h1, h2, h3, h4 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.25;
  color: var(--color-space);
}

h1 {
  font-size: clamp(28px, 4vw, 40px);
}

h2 {
  font-size: clamp(22px, 3vw, 28px);
}

h3 {
  font-size: 18px;
}

h4 {
  font-size: 16px;
}

#main-content {
  min-height: 60vh;
}

.content-container {
  width: 100%;
  max-width: var(--content-width);
  margin: 0 auto;
  padding: 0 var(--gutter);
}

.skip-link {
  position: fixed;
  top: -100%;
  left: 16px;
  z-index: 300;
  background: var(--color-cream);
  color: var(--color-space);
  padding: 8px 16px;
  border-radius: 0 0 4px 4px;
  font-size: 14px;
  font-weight: 500;
  text-decoration: none;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.25);
  transition: top 0.2s ease;
}

.skip-link:focus {
  top: 0;
}

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

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 24px;
  font-family: var(--font-heading);
  font-size: 15px;
  font-weight: 700;
  line-height: 1.4;
  border-radius: 2px;
  cursor: pointer;
  text-decoration: none;
  border: 1px solid transparent;
  transition: background 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

.btn--primary {
  background: var(--color-red);
  border-color: var(--color-red);
  color: #fff;
}

.btn--primary:hover {
  background: var(--color-orange);
  border-color: var(--color-orange);
  color: #fff;
}

.btn--ghost {
  background: transparent;
  border-color: rgba(10, 30, 60, 0.35);
  color: var(--color-space);
}

.btn--ghost:hover {
  border-color: var(--color-space);
  color: var(--color-space);
}

.btn--inverse {
  background: transparent;
  border-color: rgba(245, 240, 230, 0.4);
  color: var(--color-cream);
}

.btn--inverse:hover {
  border-color: var(--color-cream);
  color: var(--color-cream);
}

/* Breadcrumbs */
.breadcrumbs {
  margin: 0 0 24px;
  font-size: 13px;
}

.breadcrumbs__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.breadcrumbs__item {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--color-metal);
}

.breadcrumbs__item:not(:last-child)::after {
  content: "/";
  font-family: var(--font-mono);
  color: var(--color-metal);
}

.breadcrumbs__link {
  color: var(--color-space);
  text-decoration: none;
}

.breadcrumbs__link:hover {
  text-decoration: underline;
}

/* Section Index */
.section-index {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin: 0 0 16px;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--color-metal);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.section-index__num {
  padding: 2px 6px;
  font-size: 11px;
  color: var(--color-red);
  border: 1px solid rgba(201, 55, 46, 0.35);
  border-radius: 2px;
}

/* Spec Rule */
.spec-rule {
  height: 12px;
  margin: 0;
  border: 0;
  background: repeating-linear-gradient(
    90deg,
    var(--color-metal) 0 1px,
    transparent 1px 8px
  );
  opacity: 0.4;
}

/* Note Box */
.note-box {
  background: var(--color-info);
  border-left: 3px solid var(--color-red);
  padding: 16px 20px;
  margin: 24px 0;
  font-size: 14px;
}

.note-box__label {
  margin: 0 0 6px;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 700;
  color: var(--color-red);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.note-box__text {
  margin: 0;
  color: var(--color-ink);
}

/* Grid */
.site-grid {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: 24px;
}

.site-grid__span-3 { grid-column: span 3; }
.site-grid__span-4 { grid-column: span 4; }
.site-grid__span-6 { grid-column: span 6; }
.site-grid__span-8 { grid-column: span 8; }
.site-grid__span-9 { grid-column: span 9; }
.site-grid__span-12 { grid-column: span 12; }

/* Section Panels */
.section-panel {
  padding: 72px 0;
}

.section-panel--tint {
  background: var(--color-info);
}

.section-panel--dark {
  background: var(--color-space);
  color: var(--color-cream);
}

.section-panel--dark h1,
.section-panel--dark h2,
.section-panel--dark h3,
.section-panel--dark h4 {
  color: var(--color-cream);
}

/* Reveal */
[data-reveal] {
  opacity: 0;
  transform: translateY(20px);
  transition:
    opacity 0.4s var(--motion-ease),
    transform 0.4s var(--motion-ease);
  transition-delay: var(--reveal-delay, 0ms);
}

[data-reveal][data-revealed="true"] {
  opacity: 1;
  transform: translateY(0);
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: var(--header-z);
  background: var(--color-space);
  color: var(--color-cream);
}

.site-header::before {
  content: "";
  display: block;
  height: 4px;
  background:
    repeating-linear-gradient(
      90deg,
      var(--color-metal) 0 1px,
      transparent 1px 8px
    ),
    repeating-linear-gradient(
      90deg,
      rgba(201, 55, 46, 0.55) 0 2px,
      transparent 2px 40px
    );
}

.site-header__inner {
  max-width: var(--content-width);
  margin: 0 auto;
  padding: 0 var(--gutter);
}

.site-header__row {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  min-height: 72px;
  padding: 12px 0 8px;
}

.site-header__status {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 6px 0 10px;
  border-top: 1px solid rgba(217, 227, 239, 0.12);
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--color-metal);
}

.site-header__status-code {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
}

.site-header__status-code::before {
  content: "";
  display: inline-block;
  width: 6px;
  height: 6px;
  background: var(--color-orange);
}

.site-header__status-text {
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* Page Progress */
.page-progress {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 3px;
  background: var(--color-red);
  transform: scaleX(0);
  transform-origin: left center;
  z-index: 20;
}

/* Brand */
.site-brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: var(--color-cream);
  text-decoration: none;
  flex-shrink: 0;
}

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

.site-brand__icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  background: var(--color-red);
  color: #fff;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 20px;
  line-height: 1;
  border-radius: 3px;
}

.site-brand__text {
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.site-brand__name {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 18px;
  line-height: 1.2;
  color: #fff;
  letter-spacing: 0.04em;
}

.site-brand__tagline {
  font-family: var(--font-mono);
  font-size: 11px;
  line-height: 1.2;
  letter-spacing: 0.08em;
  color: var(--color-metal);
}

/* NAV */
.site-nav__list {
  display: flex;
  align-items: center;
  gap: 2px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.site-nav__link {
  display: flex;
  align-items: baseline;
  gap: 6px;
  padding: 10px 12px 14px;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 15px;
  line-height: 1.2;
  color: var(--color-cream);
  text-decoration: none;
  opacity: 0.75;
  position: relative;
  transition: opacity 0.2s ease, color 0.2s ease;
}

.site-nav__link::after {
  content: "";
  position: absolute;
  left: 12px;
  right: 12px;
  bottom: 6px;
  height: 2px;
  background: var(--color-red);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 0.25s var(--motion-ease);
}

.site-nav__link:hover {
  opacity: 1;
  color: #fff;
  text-decoration: none;
}

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

.site-nav__link[aria-current="page"] {
  opacity: 1;
  color: #fff;
}

.site-nav__link[aria-current="page"] .site-nav__index {
  color: var(--color-red);
}

.site-nav__index {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 400;
  color: var(--color-metal);
  transition: color 0.2s ease;
}

/* Nav Toggle */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 8px;
  background: none;
  border: 1px solid rgba(245, 240, 230, 0.3);
  border-radius: 2px;
  padding: 6px 12px;
  color: var(--color-cream);
  font-size: 13px;
  cursor: pointer;
  transition: border-color 0.2s ease, background 0.2s ease;
}

.nav-toggle:hover {
  border-color: var(--color-metal);
  background: rgba(245, 240, 230, 0.06);
}

.nav-toggle__bars {
  display: flex;
  flex-direction: column;
  gap: 4px;
  width: 16px;
}

.nav-toggle__bar {
  display: block;
  height: 2px;
  background: currentColor;
  transition: transform 0.25s var(--motion-ease), opacity 0.25s var(--motion-ease);
}

.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);
}

.nav-toggle__text {
  font-variant-numeric: tabular-nums;
}

/* Footer */
.site-footer {
  background: var(--color-space);
  color: var(--color-cream);
}

.site-footer::before {
  content: "";
  display: block;
  height: 4px;
  background:
    repeating-linear-gradient(
      90deg,
      var(--color-metal) 0 1px,
      transparent 1px 8px
    ),
    repeating-linear-gradient(
      90deg,
      rgba(201, 55, 46, 0.45) 0 2px,
      transparent 2px 40px
    );
}

.site-footer__inner {
  max-width: var(--content-width);
  margin: 0 auto;
  padding: 48px var(--gutter) 24px;
}

.site-footer__top {
  display: grid;
  grid-template-columns: 2fr 1.5fr 1fr;
  gap: 48px;
  padding-bottom: 32px;
}

.site-footer__block {
  min-width: 0;
}

.site-footer__desc {
  margin: 16px 0 0;
  max-width: 360px;
  font-size: 14px;
  line-height: 1.7;
  color: rgba(245, 240, 230, 0.65);
}

.site-footer__heading {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 0 0 16px;
  font-family: var(--font-heading);
  font-size: 14px;
  font-weight: 700;
  color: var(--color-cream);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.site-footer__index {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--color-red);
}

.site-footer__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 10px;
}

.site-footer__contact-item {
  display: flex;
  flex-direction: column;
  gap: 2px;
  font-size: 14px;
}

.site-footer__contact-label {
  font-family: var(--font-mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-metal);
}

.site-footer__contact-value {
  color: rgba(245, 240, 230, 0.85);
}

.site-footer__link-item {
  margin: 0;
}

.site-footer__link-item a {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: rgba(245, 240, 230, 0.85);
  font-size: 14px;
  text-decoration: none;
  transition: color 0.2s ease, padding-left 0.2s ease;
}

.site-footer__link-item a::before {
  content: "→";
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--color-metal);
  transition: color 0.2s ease;
}

.site-footer__link-item a:hover {
  color: #fff;
  padding-left: 4px;
  text-decoration: none;
}

.site-footer__link-item a:hover::before {
  color: var(--color-red);
}

.site-footer__bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
  border-top: 1px solid rgba(217, 227, 239, 0.12);
  padding-top: 16px;
  margin-top: 32px;
}

.site-footer__trust {
  max-width: 640px;
  margin: 0;
  font-size: 13px;
  line-height: 1.6;
  color: rgba(245, 240, 230, 0.55);
}

.site-footer__copyright {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--color-metal);
  white-space: nowrap;
}

.site-footer__divider {
  color: var(--color-metal);
  opacity: 0.5;
}

/* Mobile Nav */
@media (max-width: 960px) {
  .nav-toggle {
    display: inline-flex;
  }

  .site-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    z-index: var(--nav-z);
    background: var(--color-space-deep);
    border-bottom: 1px solid rgba(217, 227, 239, 0.15);
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.35);
    max-height: 0;
    overflow: hidden;
    opacity: 0;
    visibility: hidden;
    transition:
      max-height 0.3s var(--motion-ease),
      opacity 0.3s var(--motion-ease),
      visibility 0s linear 0.3s;
  }

  .site-nav[data-open="true"] {
    max-height: 440px;
    opacity: 1;
    visibility: visible;
    transition-delay: 0s;
  }

  .site-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 8px 20px 20px;
  }

  .site-nav__item {
    border-bottom: 1px solid rgba(217, 227, 239, 0.08);
  }

  .site-nav__item:last-child {
    border-bottom: 0;
  }

  .site-nav__link {
    padding: 12px 4px;
    font-size: 15px;
  }

  .site-nav__link::after {
    left: 4px;
    right: auto;
    bottom: 8px;
    width: 24px;
  }

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

/* Tablet */
@media (max-width: 900px) {
  .site-footer__top {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }

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

  .site-grid__span-3,
  .site-grid__span-4 {
    grid-column: span 6;
  }

  .site-grid__span-6,
  .site-grid__span-8,
  .site-grid__span-9 {
    grid-column: span 12;
  }

  .section-panel {
    padding: 56px 0;
  }
}

/* Mobile */
@media (max-width: 600px) {
  :root {
    --gutter: 16px;
  }

  .site-footer__top {
    grid-template-columns: 1fr;
    gap: 28px;
  }

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

  .site-header__row {
    min-height: 60px;
  }

  .site-brand__icon {
    width: 34px;
    height: 34px;
    font-size: 17px;
  }

  .site-brand__name {
    font-size: 16px;
  }

  .site-brand__tagline {
    display: none;
  }

  .site-header__status-code {
    display: none;
  }

  .site-footer__copyright {
    white-space: normal;
    flex-wrap: wrap;
  }

  .section-grid__span-3,
  .section-grid__span-4,
  .section-grid__span-6,
  .section-grid__span-8,
  .section-grid__span-9,
  .section-grid__span-12,
  .site-grid__span-3,
  .site-grid__span-4,
  .site-grid__span-6,
  .site-grid__span-8,
  .site-grid__span-9,
  .site-grid__span-12 {
    grid-column: span 12;
  }

  .btn {
    width: 100%;
  }
}

/* Reduced Motion */
@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;
    transition-delay: 0ms !important;
  }

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

  .page-progress {
    display: none;
  }
}