:root {
  --navy-950: #07162e;
  --navy-900: #0a1e40;
  --navy-700: #123b77;
  --blue-500: #1b6df2;
  --sky-400: #5fa8ff;
  --gold-400: #e3b341;
  --gold-200: #f7d98c;
  --red-500: #e63b3b;
  --cream-50: #f6f3eb;
  --muted-300: #b9c6da;
  --glass-light: rgba(255, 255, 255, 0.08);
  --font-body: "Noto Sans SC", "Source Han Sans SC", "Microsoft YaHei", -apple-system, sans-serif;
  --font-display: "Arial Black", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: "SFMono-Regular", "Roboto Mono", "Courier New", monospace;
  --rail-width: 64px;
  --header-h-mobile: 56px;
  --duration: 280ms;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}

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

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

body {
  margin: 0;
  padding-left: var(--rail-width);
  background-color: var(--navy-900);
  background-image:
    linear-gradient(rgba(95, 168, 255, 0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(95, 168, 255, 0.04) 1px, transparent 1px);
  background-size: 40px 40px;
  color: var(--cream-50);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

[hidden] {
  display: none !important;
}

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

::selection {
  background: var(--gold-400);
  color: var(--navy-950);
}

:focus-visible {
  outline: 2px solid var(--gold-400);
  outline-offset: 2px;
}

h1, h2, h3, h4 {
  font-family: var(--font-display);
  color: var(--cream-50);
  line-height: 1.25;
  margin: 0 0 0.5em;
}

h1 {
  font-size: clamp(2rem, 4vw, 3.25rem);
  letter-spacing: -0.02em;
}

h2 {
  font-size: clamp(1.5rem, 2.5vw, 2.125rem);
}

h3 {
  font-size: 1.25rem;
}

p {
  margin: 0 0 1em;
}

a {
  color: var(--blue-500);
  transition: color var(--duration) var(--ease);
}

a:hover {
  color: var(--gold-200);
}

hr {
  border: 0;
  border-top: 1px solid rgba(95, 168, 255, 0.14);
  margin: 32px 0;
}

[id] {
  scroll-margin-top: 72px;
}

.site-main,
#main-content {
  display: block;
  min-height: 60vh;
}

/* ===== Skip link ===== */
.skip-link {
  position: fixed;
  top: 12px;
  left: 12px;
  z-index: 2000;
  padding: 10px 16px;
  background: var(--gold-400);
  color: var(--navy-950);
  font-weight: 800;
  font-size: 14px;
  text-decoration: none;
  border-radius: 2px;
  opacity: 0;
  transform: translateY(-200%);
  transition: opacity var(--duration) var(--ease), transform var(--duration) var(--ease);
}

.skip-link:focus {
  opacity: 1;
  transform: translateY(0);
}

/* ===== Site header / rail ===== */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  z-index: 1000;
  width: var(--rail-width);
  display: flex;
  flex-direction: column;
  align-items: stretch;
  background: var(--navy-950);
  border-right: 1px solid rgba(95, 168, 255, 0.14);
}

.site-header::after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  left: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--gold-400), var(--blue-500) 72%, transparent);
}

.site-brand {
  display: grid;
  place-items: center;
  gap: 8px;
  padding: 18px 4px 14px;
  text-decoration: none;
  border-bottom: 1px solid rgba(95, 168, 255, 0.12);
}

.site-brand__mark {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  background: linear-gradient(135deg, var(--gold-400), var(--gold-200));
  color: var(--navy-950);
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 14px;
  line-height: 1;
  transform: skewX(-6deg);
}

.site-brand__name {
  writing-mode: vertical-rl;
  text-orientation: upright;
  font-size: 12px;
  font-weight: 900;
  letter-spacing: 0.14em;
  line-height: 1.2;
  color: var(--cream-50);
}

.site-brand__domain {
  display: none;
}

/* ===== Nav toggle ===== */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 6px;
  padding: 6px 10px;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(95, 168, 255, 0.24);
  border-radius: 2px;
  color: var(--cream-50);
  font-family: var(--font-body);
  cursor: pointer;
}

.nav-toggle__bars {
  display: inline-flex;
  flex-direction: column;
  gap: 3px;
  width: 14px;
}

.nav-toggle__bar {
  display: block;
  height: 2px;
  background: var(--gold-400);
  border-radius: 1px;
  transition: transform var(--duration) var(--ease), opacity var(--duration) var(--ease);
}

.nav-toggle__label {
  font-size: 12px;
  font-weight: 700;
  color: var(--muted-300);
}

.site-header[data-open] .nav-toggle__bar:nth-child(1) {
  transform: translateY(5px) rotate(45deg);
}

.site-header[data-open] .nav-toggle__bar:nth-child(2) {
  opacity: 0;
}

.site-header[data-open] .nav-toggle__bar:nth-child(3) {
  transform: translateY(-5px) rotate(-45deg);
}

/* ===== Site nav ===== */
.site-nav {
  flex: 1 1 auto;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  overflow-x: hidden;
  padding-bottom: 70px;
}

.site-nav__header {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  padding: 10px 0 6px;
}

.site-nav__code {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.12em;
  color: var(--sky-400);
}

.site-nav__hint {
  font-size: 9px;
  color: var(--muted-300);
}

.site-nav__list {
  list-style: none;
  margin: auto 0;
  padding: 8px 0;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.site-nav__item {
  margin: 0;
}

.site-nav__link {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1px;
  min-height: 62px;
  padding: 8px 2px;
  color: var(--muted-300);
  text-decoration: none;
  transition: color var(--duration) var(--ease), background var(--duration) var(--ease);
}

.site-nav__link::before {
  content: "";
  position: absolute;
  left: 0;
  top: 18%;
  bottom: 18%;
  width: 2px;
  background: var(--gold-400);
  opacity: 0;
  transform: scaleY(0);
  transform-origin: top center;
  transition: opacity var(--duration) var(--ease), transform var(--duration) var(--ease);
}

.site-nav__index {
  font-family: var(--font-mono);
  font-size: 9px;
  letter-spacing: 0.06em;
  color: var(--sky-400);
  transition: color var(--duration) var(--ease);
}

.site-nav__label {
  writing-mode: vertical-rl;
  text-orientation: upright;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.12em;
  line-height: 1.15;
  color: inherit;
}

.site-nav__en {
  display: none;
}

.site-nav__link:hover,
.site-nav__link:focus-visible,
.site-nav__link[aria-current="page"] {
  color: var(--gold-200);
  background: var(--glass-light);
}

.site-nav__link:hover::before,
.site-nav__link:focus-visible::before,
.site-nav__link[aria-current="page"]::before {
  opacity: 1;
  transform: scaleY(1);
}

.site-nav__link[aria-current="page"] .site-nav__index {
  color: var(--gold-400);
}

.site-nav__meta {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  margin-top: auto;
  padding: 12px 2px;
  border-top: 1px solid rgba(95, 168, 255, 0.12);
}

.site-nav__status {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-family: var(--font-mono);
  font-size: 9px;
  color: var(--muted-300);
}

.site-nav__status-dot {
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--red-500);
}

.site-nav__circle {
  display: grid;
  place-items: center;
  width: 22px;
  height: 22px;
  border: 1px solid rgba(95, 168, 255, 0.3);
  border-radius: 50%;
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--sky-400);
}

/* ===== Rail scroll progress ===== */
.site-rail-progress {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  width: 2px;
  background: rgba(95, 168, 255, 0.08);
  pointer-events: none;
  z-index: 2;
}

.site-rail-progress__bar {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  --progress: 0;
  background: linear-gradient(to bottom, var(--gold-400), var(--blue-500));
  transform: scaleY(var(--progress));
  transform-origin: top center;
  will-change: transform;
}

/* ===== Back to top ===== */
.site-backtop {
  position: absolute;
  left: 50%;
  bottom: 14px;
  z-index: 3;
  width: 44px;
  height: 44px;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 1px;
  background: rgba(18, 59, 119, 0.72);
  border: 1px solid rgba(95, 168, 255, 0.28);
  border-radius: 2px;
  color: var(--muted-300);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transition: opacity var(--duration) var(--ease), visibility var(--duration), background var(--duration) var(--ease), color var(--duration) var(--ease);
}

.site-backtop[data-visible] {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
}

.site-backtop:hover {
  background: var(--navy-700);
  border-color: rgba(227, 179, 65, 0.5);
  color: var(--gold-200);
}

.site-backtop__arrow {
  font-size: 16px;
  line-height: 1;
}

.site-backtop__label {
  font-family: var(--font-mono);
  font-size: 8px;
  letter-spacing: 0.1em;
}

/* ===== Nav overlay (mobile) ===== */
.nav-overlay {
  position: fixed;
  top: var(--header-h-mobile);
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 1001;
  background: rgba(7, 22, 46, 0.72);
  backdrop-filter: blur(2px);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--duration) var(--ease), visibility var(--duration);
}

.site-header[data-open] .nav-overlay {
  opacity: 1;
  visibility: visible;
}

/* ===== Mobile header drawer ===== */
@media (max-width: 767px) {
  body {
    padding-top: var(--header-h-mobile);
    padding-left: 0;
  }

  .site-header {
    top: 0;
    right: 0;
    bottom: auto;
    width: 100%;
    height: var(--header-h-mobile);
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    border-right: none;
    border-bottom: 1px solid rgba(95, 168, 255, 0.14);
  }

  .site-header::after {
    height: 3px;
  }

  .site-brand {
    display: flex;
    flex-direction: row;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    border-bottom: none;
  }

  .site-brand__mark {
    width: 28px;
    height: 28px;
    font-size: 11px;
  }

  .site-brand__name {
    writing-mode: horizontal-tb;
    font-size: 15px;
    letter-spacing: 0.02em;
  }

  .site-brand__domain {
    display: block;
    font-family: var(--font-mono);
    font-size: 10px;
    color: var(--muted-300);
  }

  .nav-toggle {
    display: inline-flex;
    margin-right: 12px;
  }

  .site-nav {
    position: fixed;
    top: var(--header-h-mobile);
    left: 0;
    bottom: 0;
    z-index: 1002;
    width: 280px;
    flex: initial;
    padding: 16px;
    background: var(--navy-950);
    border-right: 1px solid rgba(95, 168, 255, 0.16);
    box-shadow: 16px 0 40px rgba(0, 0, 0, 0.42);
    transform: translateX(-105%);
    visibility: hidden;
    transition: transform var(--duration) var(--ease), visibility 0s var(--duration);
  }

  .site-header[data-open] .site-nav {
    transform: translateX(0);
    visibility: visible;
    transition: transform var(--duration) var(--ease);
  }

  .site-nav__header {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    padding: 2px 2px 12px;
  }

  .site-nav__hint {
    display: none;
  }

  .site-nav__list {
    margin: 0;
    gap: 4px;
  }

  .site-nav__link {
    flex-direction: row;
    align-items: center;
    gap: 12px;
    min-height: 44px;
    padding: 10px 12px;
  }

  .site-nav__index {
    min-width: 24px;
    font-size: 11px;
  }

  .site-nav__label {
    writing-mode: horizontal-tb;
    font-size: 16px;
    letter-spacing: 0.02em;
  }

  .site-nav__en {
    display: block;
    margin-left: auto;
    font-family: var(--font-mono);
    font-size: 10px;
    color: var(--muted-300);
  }

  .site-nav__meta {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    margin-top: auto;
    padding: 12px 4px 0;
  }

  .site-nav__circle {
    display: none;
  }

  .site-rail-progress {
    top: auto;
    right: 0;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 2px;
  }

  .site-rail-progress__bar {
    width: 100%;
    height: 100%;
    transform: scaleX(var(--progress));
    transform-origin: left center;
    background: linear-gradient(to right, var(--gold-400), var(--blue-500));
  }

  .site-backtop {
    position: fixed;
    left: auto;
    right: 16px;
    bottom: 20px;
    width: 42px;
    height: 42px;
    transform: none;
    background: rgba(7, 22, 46, 0.9);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.44);
  }
}

@media (max-width: 400px) {
  .site-brand__domain {
    display: none;
  }
}

/* ===== Footer ===== */
.site-footer {
  background: var(--navy-950);
  border-top: 1px solid rgba(95, 168, 255, 0.14);
  padding: 48px 0 0;
}

.site-footer__grid {
  max-width: 1200px;
  margin-inline: auto;
  padding: 0 24px 40px;
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr 1.2fr;
  gap: 40px;
}

.site-footer__block--brand {
  padding: 20px;
  background: var(--glass-light);
  border: 1px solid rgba(95, 168, 255, 0.12);
  border-radius: 4px;
}

.site-footer__heading {
  margin: 0 0 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid rgba(95, 168, 255, 0.14);
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 400;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--sky-400);
}

.site-footer__heading::before {
  content: attr(data-block-index);
  margin-right: 8px;
  color: var(--gold-400);
}

.site-footer__brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 14px;
  text-decoration: none;
}

.site-footer__mark {
  display: grid;
  place-items: center;
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--gold-400), var(--gold-200));
  color: var(--navy-950);
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 15px;
  line-height: 1;
  transform: skewX(-6deg);
}

.site-footer__brand-copy {
  display: block;
}

.site-footer__name {
  display: block;
  color: var(--cream-50);
  font-family: var(--font-display);
  font-size: 18px;
  font-weight: 900;
  line-height: 1.2;
}

.site-footer__domain {
  display: block;
  margin-top: 2px;
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--muted-300);
}

.site-footer__tagline {
  margin: 0 0 12px;
  color: var(--gold-200);
  font-size: 15px;
  font-weight: 700;
}

.site-footer__trust {
  margin: 0;
  max-width: 46ch;
  font-size: 14px;
  line-height: 1.8;
  color: var(--muted-300);
}

.site-footer__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 8px;
}

.site-footer__list a {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--muted-300);
  font-size: 14px;
  text-decoration: none;
  transition: color var(--duration) var(--ease), padding-left var(--duration) var(--ease);
}

.site-footer__list a::before {
  content: "›";
  font-family: var(--font-mono);
  color: var(--sky-400);
  transition: color var(--duration) var(--ease);
}

.site-footer__list a:hover {
  padding-left: 4px;
  color: var(--gold-200);
}

.site-footer__dl {
  margin: 0;
  display: grid;
  gap: 12px;
}

.site-footer__contact-row {
  display: grid;
  gap: 2px;
}

.site-footer__dl dt {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--sky-400);
}

.site-footer__dl dd {
  margin: 0;
  font-size: 14px;
  line-height: 1.5;
  color: var(--cream-50);
  word-break: break-all;
}

.site-footer__bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 18px 24px;
  border-top: 1px solid rgba(95, 168, 255, 0.14);
  background: rgba(7, 22, 46, 0.7);
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--muted-300);
}

.site-footer__copy {
  color: var(--gold-200);
}

/* ===== Shared layout components ===== */
.container {
  width: 100%;
  max-width: 1200px;
  margin-inline: auto;
  padding-inline: 24px;
}

@media (max-width: 767px) {
  .container {
    padding-inline: 16px;
  }
}

.section {
  padding-block: 48px;
}

.section__code {
  display: block;
  margin-bottom: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--sky-400);
}

.kicker {
  display: block;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--sky-400);
}

.lead {
  max-width: 60ch;
  font-size: 1.125rem;
  color: var(--muted-300);
}

.mono {
  font-family: var(--font-mono);
  font-size: 13px;
}

.text-muted {
  color: var(--muted-300);
}

.text-gold {
  color: var(--gold-200);
}

.prose {
  max-width: 72ch;
}

.grid {
  display: grid;
  gap: 24px;
}

.grid--split {
  grid-template-columns: 1.4fr 1fr;
}

.grid--3 {
  grid-template-columns: repeat(3, 1fr);
}

.grid--4 {
  grid-template-columns: repeat(4, 1fr);
}

@media (max-width: 1023px) {
  .grid--4 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 767px) {
  .grid--split,
  .grid--3,
  .grid--4 {
    grid-template-columns: 1fr;
  }
}

.panel {
  padding: 24px;
  background: var(--glass-light);
  border: 1px solid rgba(95, 168, 255, 0.16);
  border-radius: 4px;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 22px;
  border: 1px solid transparent;
  border-radius: 2px;
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 700;
  line-height: 1.2;
  text-decoration: none;
  cursor: pointer;
  transition: background var(--duration) var(--ease), color var(--duration) var(--ease), border-color var(--duration) var(--ease), transform var(--duration) var(--ease);
}

.btn--gold {
  background: var(--gold-400);
  color: var(--navy-950);
}

.btn--gold:hover {
  background: var(--gold-200);
  color: var(--navy-950);
  transform: translateY(-2px);
}

.btn--ghost {
  background: transparent;
  color: var(--gold-200);
  border-color: rgba(227, 179, 65, 0.5);
}

.btn--ghost:hover {
  background: rgba(227, 179, 65, 0.08);
  border-color: var(--gold-400);
  color: var(--gold-200);
}

.btn--sm {
  padding: 6px 14px;
  font-size: 13px;
}

/* ===== Breadcrumb ===== */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0;
  padding: 12px 0;
  list-style: none;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--muted-300);
}

.breadcrumb li + li::before {
  content: "/";
  margin-right: 8px;
  color: var(--sky-400);
}

.breadcrumb a {
  color: var(--muted-300);
  text-decoration: none;
}

.breadcrumb a:hover {
  color: var(--gold-200);
}

.breadcrumb [aria-current="page"] {
  color: var(--gold-400);
}

/* ===== Image frame ===== */
.image-frame {
  position: relative;
  display: block;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background-color: var(--navy-700);
  background-image:
    linear-gradient(45deg, rgba(95, 168, 255, 0.08) 25%, transparent 25%, transparent 75%, rgba(95, 168, 255, 0.08) 75%),
    linear-gradient(45deg, rgba(95, 168, 255, 0.08) 25%, transparent 25%, transparent 75%, rgba(95, 168, 255, 0.08) 75%);
  background-size: 24px 24px, 24px 24px;
  background-position: 0 0, 12px 12px;
}

.image-frame::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 40%;
  height: 3px;
  background: linear-gradient(90deg, var(--gold-400), transparent);
}

.image-frame[data-frame="wide"] {
  aspect-ratio: 21 / 9;
}

.image-frame[data-frame="square"] {
  aspect-ratio: 1 / 1;
}

.image-frame[data-frame="portrait"] {
  aspect-ratio: 3 / 4;
}

.figure {
  margin: 0;
}

.figure__caption {
  margin-top: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--muted-300);
}

@media (max-width: 1023px) {
  .site-footer__grid {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }
}

@media (max-width: 767px) {
  .site-footer {
    padding-top: 32px;
  }

  .site-footer__grid {
    grid-template-columns: 1fr;
    gap: 28px;
    padding: 0 16px 24px;
  }

  .site-footer__bar {
    flex-direction: column;
    align-items: flex-start;
    padding: 16px;
  }

  .section {
    padding-block: 32px;
  }
}

@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;
  }
}