:root {
  --color-deep: #0A1F3C;
  --color-gold: #C9A227;
  --color-red: #B23A48;
  --color-deep-gray: #112B4F;
  --color-electric: #00D2DF;
  --color-purple: #7A6FF0;
  --color-warmwhite: #FDFCF8;
  --color-lighttexture: #F4F1EA;
  --color-ink: #1B1B1B;
  --color-mercury: #F0F0F0;
  --font-title: "Noto Serif SC", "Songti SC", serif;
  --font-body: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-number: "Roboto Mono", "SFMono-Regular", Consolas, monospace;
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 2rem;
  --space-xl: 4rem;
  --container-max: 1280px;
  --radius-sm: 6px;
  --radius-lg: 24px;
  --radius-organic: 4px 20px 4px 20px;
  --header-height: 72px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Reset & Base */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-body);
  background-color: var(--color-warmwhite);
  color: var(--color-ink);
  line-height: 1.7;
  min-height: 100vh;
}

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

a {
  color: var(--color-deep);
  text-decoration: none;
  transition: color var(--transition);
}

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

ul,
ol {
  list-style: none;
}

h1,
h2,
h3 {
  font-family: var(--font-title);
  line-height: 1.3;
  color: var(--color-deep);
}

h1 {
  font-size: clamp(2.5rem, 6vw, 4.5rem);
  font-weight: 700;
  letter-spacing: 0.02em;
}

h2 {
  font-size: clamp(1.75rem, 3vw, 2.5rem);
  font-weight: 600;
}

h3 {
  font-size: 1.25rem;
  font-weight: 600;
}

::selection {
  background: var(--color-gold);
  color: var(--color-deep);
}

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

/* Utility Classes */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.container {
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--space-lg);
}

.skip-link {
  position: fixed;
  top: -100%;
  left: var(--space-md);
  z-index: 1000;
  background: var(--color-deep);
  color: var(--color-warmwhite);
  padding: var(--space-sm) var(--space-lg);
  border-radius: var(--radius-sm);
  font-weight: 600;
  transition: top 0.2s;
}

.skip-link:focus {
  top: var(--space-md);
  color: var(--color-gold);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 0.6em 1.4em;
  border-radius: 999px;
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.95rem;
  line-height: 1.4;
  border: 1.5px solid transparent;
  cursor: pointer;
  transition: all var(--transition);
  text-align: center;
}

.btn--primary {
  background: var(--color-gold);
  color: var(--color-deep);
  border-color: var(--color-gold);
}

.btn--primary:hover {
  background: transparent;
  color: var(--color-gold);
}

.btn--outline {
  background: transparent;
  color: var(--color-deep);
  border-color: var(--color-deep);
}

.btn--outline:hover {
  background: var(--color-deep);
  color: var(--color-warmwhite);
}

.btn--link {
  background: none;
  padding: 0;
  border-radius: 0;
  color: var(--color-electric);
  border-bottom: 1px solid var(--color-electric);
}

/* Header & Navigation */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  padding-block: var(--space-md);
  background: transparent;
  pointer-events: none;
}

.site-header__inner {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: var(--space-md);
  pointer-events: auto;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-md);
  width: fit-content;
}

.brand__mark {
  font-family: var(--font-number);
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--color-gold);
  background: var(--color-deep);
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-organic);
  line-height: 1;
  border: 1px solid rgba(201, 162, 39, 0.4);
}

.brand__text {
  display: flex;
  flex-direction: column;
  line-height: 1.2;
}

.brand__name {
  font-family: var(--font-title);
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--color-deep);
  letter-spacing: 0.08em;
}

.brand__sub {
  font-size: 0.7rem;
  color: var(--color-deep-gray);
  letter-spacing: 0.15em;
  text-transform: uppercase;
}

.floating-nav {
  background: rgba(10, 31, 60, 0.9);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-radius: 999px;
  padding: var(--space-xs);
  border: 1px solid rgba(201, 162, 39, 0.25);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.25);
}

.floating-nav__list {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.floating-nav__link {
  display: block;
  padding: 0.5em 1.2em;
  border-radius: 999px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-mercury);
  white-space: nowrap;
  transition: background var(--transition), color var(--transition);
}

.floating-nav__link:hover {
  background: rgba(255, 255, 255, 0.1);
  color: var(--color-gold);
}

.floating-nav__link[aria-current="page"] {
  background: var(--color-gold);
  color: var(--color-deep);
  font-weight: 700;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 44px;
  height: 44px;
  padding: 10px;
  background: var(--color-deep);
  border-radius: 50%;
  border: none;
  cursor: pointer;
  justify-self: end;
}

.nav-toggle__bar {
  display: block;
  height: 2px;
  width: 100%;
  background: var(--color-gold);
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}

.nav-toggle.is-active .nav-toggle__bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle.is-active .nav-toggle__bar:nth-child(2) {
  opacity: 0;
}

.nav-toggle.is-active .nav-toggle__bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Footer */
.site-footer {
  background: var(--color-deep);
  color: var(--color-mercury);
  padding-top: var(--space-xl);
  margin-top: var(--space-xl);
  position: relative;
  overflow: hidden;
}

.site-footer::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(201, 162, 39, 0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(201, 162, 39, 0.05) 1px, transparent 1px);
  background-size: 40px 40px;
  pointer-events: none;
}

.site-footer__grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1.2fr;
  gap: var(--space-xl);
  position: relative;
  padding-bottom: var(--space-xl);
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.site-footer__brand {
  font-family: var(--font-title);
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--color-warmwhite);
  margin-bottom: var(--space-sm);
}

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

.site-footer__desc {
  color: rgba(240, 240, 240, 0.8);
  font-size: 0.95rem;
  max-width: 40ch;
  margin-bottom: var(--space-md);
}

.site-footer__trust {
  font-size: 0.85rem;
  color: rgba(240, 240, 240, 0.6);
  border-left: 3px solid var(--color-gold);
  padding-left: var(--space-md);
  max-width: 45ch;
}

.site-footer__title {
  color: var(--color-gold);
  font-size: 1rem;
  margin-bottom: var(--space-lg);
  letter-spacing: 0.1em;
  position: relative;
  padding-bottom: var(--space-xs);
}

.site-footer__title::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 32px;
  height: 2px;
  background: var(--color-gold);
}

.site-footer__list {
  display: grid;
  gap: var(--space-sm);
}

.site-footer__list a {
  color: rgba(240, 240, 240, 0.8);
  font-size: 0.9rem;
  transition: color var(--transition), padding-left var(--transition);
}

.site-footer__list a:hover {
  color: var(--color-gold);
  padding-left: var(--space-xs);
}

.site-footer__list--contact li {
  font-size: 0.9rem;
  color: var(--color-mercury);
  padding-left: var(--space-md);
  position: relative;
}

.site-footer__list--contact li::before {
  content: "◆";
  position: absolute;
  left: 0;
  color: var(--color-gold);
  font-size: 0.6rem;
  top: 0.3em;
}

.site-footer__list--contact span {
  color: rgba(240, 240, 240, 0.5);
}

.site-footer__legal {
  margin-top: var(--space-lg);
  display: flex;
  gap: var(--space-md);
  align-items: center;
}

.site-footer__legal a {
  color: var(--color-electric);
  font-size: 0.9rem;
}

.site-footer__bottom {
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-sm);
  padding-block: var(--space-lg);
  font-size: 0.8rem;
  color: rgba(240, 240, 240, 0.4);
  position: relative;
}

/* Layouts & Grid */
.grid {
  display: grid;
  gap: var(--space-lg);
}

.grid--2 {
  grid-template-columns: repeat(2, 1fr);
}

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

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

/* Cards */
.card {
  background: var(--color-warmwhite);
  border-radius: var(--radius-organic);
  padding: var(--space-lg);
  box-shadow: 0 4px 20px rgba(10, 31, 60, 0.06);
  border: 1px solid rgba(10, 31, 60, 0.05);
  transition: transform var(--transition), box-shadow var(--transition);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(10, 31, 60, 0.1);
}

.card--main {
  background: linear-gradient(145deg, var(--color-deep), var(--color-deep-gray));
  color: var(--color-mercury);
  border: none;
}

.card--main h1,
.card--main h2,
.card--main h3 {
  color: var(--color-warmwhite);
}

.card--aside {
  background: var(--color-lighttexture);
  border-left: 4px solid var(--color-gold);
}

.card--highlight {
  border-top: 4px solid var(--color-red);
}

/* Section Titles */
.section-title {
  display: flex;
  align-items: baseline;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.section-title__index {
  font-family: var(--font-number);
  font-size: 1.2rem;
  color: var(--color-gold);
  font-weight: 700;
  letter-spacing: 0.1em;
}

.section-title__text {
  font-size: inherit;
}

/* Breadcrumbs */
.breadcrumbs {
  margin-bottom: var(--space-lg);
  font-size: 0.9rem;
}

.breadcrumbs__list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
  color: var(--color-deep-gray);
}

.breadcrumbs__item + .breadcrumbs__item::before {
  content: "/";
  margin-right: var(--space-xs);
  color: var(--color-gold);
}

.breadcrumbs__item a {
  color: var(--color-deep-gray);
}

.breadcrumbs__item[aria-current="page"] {
  color: var(--color-ink);
  font-weight: 600;
}

/* Timeline */
.timeline {
  position: relative;
  padding-left: var(--space-lg);
}

.timeline::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 2px;
  background: linear-gradient(to bottom, var(--color-gold), var(--color-deep-gray), transparent);
}

.timeline__item {
  position: relative;
  margin-bottom: var(--space-lg);
}

.timeline__item::before {
  content: "";
  position: absolute;
  left: calc(-1 * var(--space-lg) + 4px);
  top: 0.5em;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-gold);
  border: 2px solid var(--color-warmwhite);
  box-shadow: 0 0 0 2px var(--color-gold);
}

.timeline__year {
  font-family: var(--font-number);
  font-size: 1rem;
  color: var(--color-gold);
  font-weight: 700;
}

.timeline__content {
  background: var(--color-warmwhite);
  padding: var(--space-md);
  border-radius: var(--radius-sm);
  margin-top: var(--space-xs);
  border: 1px solid var(--color-lighttexture);
}

/* Legend / Filter */
.legend {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  padding: var(--space-md);
  background: var(--color-lighttexture);
  border-radius: var(--radius-lg);
  border: 1px solid rgba(201, 162, 39, 0.3);
  margin-bottom: var(--space-lg);
}

.legend__item {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
}

.legend__key {
  width: 12px;
  height: 12px;
  border-radius: 2px;
}

.legend__btn {
  background: none;
  border: none;
  cursor: pointer;
  font-family: var(--font-body);
  font-size: 0.9rem;
  color: var(--color-deep);
  padding: var(--space-xs) var(--space-sm);
  border-radius: 999px;
  transition: all var(--transition);
}

.legend__btn:hover {
  background: var(--color-warmwhite);
}

.legend__btn.is-active {
  background: var(--color-deep);
  color: var(--color-gold);
}

/* Image Placeholder */
.image-placeholder {
  aspect-ratio: var(--ratio, 4 / 3);
  width: 100%;
  background: linear-gradient(145deg, var(--color-deep-gray), var(--color-deep));
  border: 1px dashed rgba(201, 162, 39, 0.5);
  border-radius: var(--radius-organic);
  position: relative;
  overflow: hidden;
}

.image-placeholder::after {
  content: attr(data-label);
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-number);
  font-size: 0.9rem;
  color: rgba(201, 162, 39, 0.7);
  background: linear-gradient(45deg, transparent 40%, rgba(0, 210, 223, 0.05) 100%);
}

/* Data Table */
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
  background: var(--color-warmwhite);
  border-radius: var(--radius-sm);
  overflow: hidden;
  box-shadow: 0 4px 20px rgba(10, 31, 60, 0.06);
}

.data-table thead {
  background: var(--color-deep);
  color: var(--color-mercury);
}

.data-table th,
.data-table td {
  padding: var(--space-sm) var(--space-md);
  text-align: left;
}

.data-table th {
  font-family: var(--font-number);
  font-weight: 600;
  font-size: 0.85rem;
  letter-spacing: 0.05em;
}

.data-table td {
  font-family: var(--font-number);
  border-bottom: 1px solid var(--color-lighttexture);
}

.data-table tbody tr:nth-child(even) {
  background: var(--color-lighttexture);
}

.data-table tbody tr:hover {
  background: rgba(0, 210, 223, 0.08);
}

/* Accordion */
.accordion__item {
  border: 1px solid var(--color-lighttexture);
  border-radius: var(--radius-sm);
  margin-bottom: var(--space-sm);
  background: var(--color-warmwhite);
}

.accordion__trigger {
  width: 100%;
  background: none;
  border: none;
  text-align: left;
  padding: var(--space-md);
  font-family: var(--font-title);
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-deep);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  gap: var(--space-md);
}

.accordion__trigger::after {
  content: "+";
  font-family: var(--font-number);
  color: var(--color-gold);
  font-size: 1.5rem;
  line-height: 1;
  transition: transform var(--transition);
}

.accordion__item.is-open .accordion__trigger::after {
  transform: rotate(45deg);
}

.accordion__panel {
  padding: 0 var(--space-md) var(--space-md);
  display: none;
  color: var(--color-ink);
  font-size: 0.95rem;
}

.accordion__item.is-open .accordion__panel {
  display: block;
  animation: fadeInUp 0.3s ease-out;
}

/* Collage */
.collage {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-auto-rows: minmax(160px, auto);
  gap: var(--space-md);
}

.collage__item--lg {
  grid-column: span 2;
  grid-row: span 2;
}

.collage__item--sm {
  grid-column: span 1;
  grid-row: span 1;
}

.collage__item--wide {
  grid-column: span 2;
  grid-row: span 1;
}

/* Back Top */
.back-top {
  position: fixed;
  right: var(--space-lg);
  bottom: var(--space-lg);
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--color-deep);
  color: var(--color-gold);
  border: 1px solid rgba(201, 162, 39, 0.5);
  font-size: 1.5rem;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
  transition: all var(--transition);
  z-index: 99;
}

.back-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-top:hover {
  background: var(--color-gold);
  color: var(--color-deep);
}

/* Responsive Breakpoints */
@media (max-width: 1024px) {
  .grid--aside,
  .grid--3 {
    grid-template-columns: 1fr;
  }

  .site-footer__grid {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-lg);
  }

  .site-footer__about {
    grid-column: 1 / -1;
  }
}

@media (max-width: 768px) {
  .container {
    padding-inline: var(--space-md);
  }

  .site-header__inner {
    grid-template-columns: 1fr auto;
  }

  .site-header {
    pointer-events: none;
  }

  .site-header__inner,
  .brand,
  .nav-toggle {
    pointer-events: auto;
  }

  .floating-nav {
    position: fixed;
    top: calc(var(--header-height) + 1rem);
    left: var(--space-md);
    right: var(--space-md);
    border-radius: var(--radius-lg);
    background: rgba(10, 31, 60, 0.96);
    padding: var(--space-md);
    transform: translateY(-150%);
    opacity: 0;
    transition: transform 0.4s ease, opacity 0.4s ease;
    border: 1px solid rgba(201, 162, 39, 0.3);
  }

  .floating-nav.is-open {
    transform: translateY(0);
    opacity: 1;
  }

  .floating-nav__list {
    flex-direction: column;
    align-items: stretch;
  }

  .floating-nav__link {
    padding: var(--space-sm);
    text-align: center;
  }

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

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

  .collage {
    grid-template-columns: 1fr 1fr;
  }

  .site-footer__grid {
    grid-template-columns: 1fr;
  }

  .site-footer__bottom {
    flex-direction: column;
    text-align: center;
  }

  .back-top {
    right: var(--space-md);
    bottom: var(--space-md);
  }
}

@media (max-width: 480px) {
  h1 {
    font-size: 2rem;
  }

  .collage {
    grid-template-columns: 1fr;
  }

  .collage__item--lg,
  .collage__item--sm,
  .collage__item--wide {
    grid-column: span 1;
    grid-row: span 1;
  }
}

/* Animations & Reduced Motion */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@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;
  }

  .card:hover {
    transform: none;
  }
}