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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 5.5rem;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.75;
  color: var(--color-text);
  background-color: var(--color-bg);
  background-image:
    radial-gradient(circle at 85% 10%, rgba(255, 201, 56, .10), transparent 30rem),
    radial-gradient(circle at 10% 30%, rgba(63, 167, 255, .08), transparent 26rem),
    linear-gradient(rgba(31, 58, 95, .16) 1px, transparent 1px),
    linear-gradient(90deg, rgba(31, 58, 95, .16) 1px, transparent 1px);
  background-size: auto, auto, 4rem 4rem, 4rem 4rem;
  overflow-x: hidden;
}

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

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-title);
  font-weight: 900;
  line-height: 1.2;
  margin-bottom: .75em;
}

p {
  margin-bottom: 1rem;
}

ul,
ol {
  margin-bottom: 1rem;
  padding-left: 1.25rem;
}

a {
  color: var(--color-link);
  text-decoration-thickness: 1px;
  text-underline-offset: .15em;
}

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

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

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

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

#main-content {
  display: block;
  min-height: 60vh;
  outline: none;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  left: 1.5rem;
  top: -100%;
  z-index: 300;
  padding: .75rem 1.25rem;
  background: var(--color-gold);
  color: var(--color-bg);
  font-weight: 600;
  text-decoration: none;
  border-radius: .5rem;
  transition: top .2s ease;
}

.skip-link:focus {
  top: 1rem;
}

[hidden] {
  display: none !important;
}

/* ===== Variables ===== */
:root {
  --color-bg: #0B1026;
  --color-bg-deep: #090D1A;
  --color-gold: #FFC938;
  --color-red: #D62828;
  --color-white: #FFFFFF;
  --color-text: #FFFFFF;
  --color-muted: #C7D0DD;
  --color-link: #3FA7FF;
  --color-success: #3DDC84;
  --color-warning: #FF8C00;
  --color-line: #1F3A5F;
  --color-panel: #F5F7FA;
  --font-title: 'Source Han Serif SC', 'Noto Serif SC', 'SimSun', serif;
  --font-body: 'Source Han Sans SC', 'Noto Sans SC', 'Helvetica Neue', Arial, sans-serif;
  --font-number: 'Roboto Mono', 'Source Code Pro', 'Courier New', monospace;
  --container: 76rem;
  --space-section: clamp(3rem, 8vw, 6rem);
  --shadow: 0 1rem 3rem rgba(0, 0, 0, .35);
}

/* ===== Base layout ===== */
.container,
.container-narrow {
  width: min(var(--container), calc(100% - 2rem));
  margin-inline: auto;
}

.container-narrow {
  width: min(48rem, calc(100% - 2rem));
}

.section {
  padding-block: var(--space-section);
  border-top: 1px solid var(--color-line);
}

.section-heading {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 1rem;
  align-items: end;
  margin-bottom: clamp(1.5rem, 4vw, 3rem);
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--color-line);
}

.section-index {
  font-family: var(--font-number);
  font-size: 1rem;
  color: var(--color-gold);
  padding-bottom: .35rem;
  border-bottom: 2px solid var(--color-gold);
}

.section-title {
  font-size: clamp(2.25rem, 5vw, 4rem);
  margin: 0;
  letter-spacing: .02em;
}

.section-heading-note {
  grid-column: 1 / -1;
  color: var(--color-muted);
  font-size: .875rem;
  border-top: 1px solid var(--color-line);
  padding-top: .5rem;
}

.rotated-note {
  display: inline-block;
  writing-mode: vertical-rl;
  text-orientation: mixed;
  font-size: .625rem;
  letter-spacing: .3em;
  line-height: 1;
  max-height: 8em;
  color: var(--color-muted);
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: .5rem;
  padding: .75rem 1.5rem;
  font-family: var(--font-body);
  font-size: .875rem;
  font-weight: 600;
  letter-spacing: .08em;
  color: var(--color-bg);
  background: var(--color-gold);
  border: 1px solid var(--color-gold);
  border-radius: 2rem;
  text-decoration: none;
  cursor: pointer;
  transition: transform .2s ease, box-shadow .2s ease, background .2s ease, color .2s ease;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 .75rem 1.5rem rgba(255, 201, 56, .18);
  background: #FFD75E;
  color: var(--color-bg);
}

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

.btn-primary:hover {
  background: #FFD75E;
  border-color: #FFD75E;
  color: var(--color-bg);
}

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

.btn-outline:hover {
  border-color: var(--color-gold);
  color: var(--color-gold);
  background: rgba(255, 201, 56, .06);
  box-shadow: none;
}

/* ===== Breadcrumb ===== */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .5rem;
  list-style: none;
  margin: 0 0 2rem;
  padding: 0;
  font-size: .75rem;
  color: var(--color-muted);
}

.breadcrumb li + li::before {
  content: "/";
  color: var(--color-line);
  margin-right: .5rem;
}

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

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

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

/* ===== Grids and cards ===== */
.grid-2 {
  display: grid;
  gap: 1.5rem;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 18rem), 1fr));
}

.grid-3 {
  display: grid;
  gap: 1.5rem;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 14rem), 1fr));
}

.card {
  background: rgba(255, 255, 255, .03);
  border: 1px solid var(--color-line);
  border-top: 3px solid var(--color-gold);
  padding: 1.5rem;
  box-shadow: 0 .5rem 1.5rem rgba(0, 0, 0, .15);
}

.panel-light {
  background: var(--color-panel);
  color: var(--color-bg-deep);
  padding: 2rem;
  border-radius: 1rem;
}

.panel-light .section-title,
.panel-light h1,
.panel-light h2,
.panel-light h3,
.panel-light h4 {
  color: var(--color-bg-deep);
}

/* ===== Media frame ===== */
.media-frame {
  position: relative;
  overflow: hidden;
  aspect-ratio: 4 / 3;
  border: 1px solid var(--color-line);
  background:
    radial-gradient(circle at 70% 20%, rgba(255, 201, 56, .12), transparent 18%),
    radial-gradient(circle at 20% 80%, rgba(63, 167, 255, .10), transparent 22%),
    linear-gradient(135deg, rgba(255, 201, 56, .06) 25%, transparent 25%),
    var(--color-bg-deep);
  background-size: auto, auto, 2rem 2rem, auto;
}

.media-frame::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 1;
  background-image:
    linear-gradient(rgba(31, 58, 95, .3) 1px, transparent 1px),
    linear-gradient(90deg, rgba(31, 58, 95, .3) 1px, transparent 1px);
  background-size: 1.5rem 1.5rem;
  mix-blend-mode: screen;
  pointer-events: none;
}

.media-frame::after {
  content: "";
  position: absolute;
  right: .75rem;
  top: .75rem;
  width: 2.5rem;
  height: 2.5rem;
  border-right: 2px solid var(--color-gold);
  border-top: 2px solid var(--color-gold);
  opacity: .6;
  z-index: 2;
  pointer-events: none;
}

.media-caption {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: .5rem;
  font-size: .75rem;
  color: var(--color-muted);
}

/* ===== Data table ===== */
.table-scroll {
  overflow-x: auto;
}

.data-table {
  width: 100%;
  min-width: 32rem;
  border-collapse: collapse;
  font-family: var(--font-number);
  font-size: .875rem;
}

.data-table th,
.data-table td {
  padding: .75rem .5rem;
  border-bottom: 1px solid var(--color-line);
  text-align: left;
}

.data-table th {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: .6875rem;
  letter-spacing: .08em;
  color: var(--color-muted);
  border-bottom-color: var(--color-gold);
  text-transform: uppercase;
}

.data-table td {
  color: var(--color-white);
}

.data-table .data-highlight {
  color: var(--color-gold);
  font-weight: 700;
}

/* ===== Notice ===== */
.notice {
  border: 1px solid var(--color-line);
  border-left: 4px solid var(--color-link);
  background: rgba(63, 167, 255, .06);
  padding: 1rem 1.25rem;
  margin-bottom: 1.5rem;
  font-size: .875rem;
}

/* ===== Study board ===== */
.study-board {
  position: relative;
  border: 1px solid var(--color-line);
  border-left: 3px solid var(--color-gold);
  background:
    linear-gradient(135deg, rgba(255, 201, 56, .06), transparent 40%),
    rgba(255, 255, 255, .02);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
}

.study-board-index {
  position: absolute;
  top: -.65rem;
  right: 1rem;
  background: var(--color-bg);
  color: var(--color-gold);
  font-family: var(--font-number);
  font-size: .75rem;
  padding: 0 .5rem;
  border: 1px solid var(--color-line);
}

.study-board h3 {
  margin-bottom: .5rem;
}

.study-board p {
  color: var(--color-muted);
  font-size: .875rem;
}

/* ===== Header ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  padding: .5rem clamp(.75rem, 3vw, 2rem);
  pointer-events: none;
}

.site-header > * {
  pointer-events: auto;
}

.nav-shell {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 1rem;
  max-width: var(--container);
  min-height: 3.5rem;
  margin: 0 auto;
  padding: .5rem 1rem;
  background: rgba(11, 16, 38, .82);
  border: 1px solid var(--color-line);
  border-radius: 3rem;
  box-shadow: var(--shadow);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
}

.brand {
  display: flex;
  flex-shrink: 0;
  align-items: center;
  gap: .75rem;
  text-decoration: none;
  color: var(--color-white);
}

.brand-mark {
  font-family: var(--font-title);
  font-size: 1.65rem;
  font-weight: 900;
  line-height: 1;
  letter-spacing: .08em;
  color: var(--color-gold);
  padding-right: .75rem;
  border-right: 1px solid var(--color-line);
}

.brand-sub {
  writing-mode: vertical-rl;
  text-orientation: mixed;
  height: 2.6rem;
  font-size: .625rem;
  letter-spacing: .3em;
  color: var(--color-muted);
  padding-left: .4rem;
}

.nav-main {
  flex: 1 1 auto;
  min-width: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.nav-list {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: .25rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-link {
  position: relative;
  display: inline-block;
  padding: .5rem .75rem;
  color: var(--color-muted);
  font-size: .875rem;
  letter-spacing: .08em;
  text-decoration: none;
  transition: color .2s ease;
}

.nav-link::after {
  content: "";
  position: absolute;
  inset-inline: .75rem;
  bottom: .25rem;
  height: 2px;
  background: var(--color-gold);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform .2s ease;
}

.nav-link:hover,
.nav-link:focus-visible {
  color: var(--color-white);
}

.nav-link:hover::after,
.nav-link:focus-visible::after,
.nav-link[aria-current="page"]::after {
  transform: scaleX(1);
}

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

.nav-actions {
  display: flex;
  flex-shrink: 0;
  align-items: center;
  gap: .5rem;
  margin-left: .25rem;
}

.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: .25rem;
  padding: .35rem .75rem;
  background: rgba(255, 255, 255, .02);
  border: 1px solid var(--color-line);
  border-radius: 2rem;
  color: var(--color-muted);
  font-size: .75rem;
  cursor: pointer;
  transition: color .2s ease, border-color .2s ease, background .2s ease;
}

.icon-btn:hover,
.icon-btn[aria-expanded="true"],
.icon-btn[aria-pressed="true"] {
  color: var(--color-gold);
  border-color: var(--color-gold);
  background: rgba(255, 201, 56, .08);
}

.nav-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  padding: .35rem;
  background: transparent;
  border: 1px solid var(--color-line);
  border-radius: 50%;
  color: var(--color-muted);
  cursor: pointer;
  transition: color .2s ease, border-color .2s ease, background .2s ease;
}

.nav-toggle:hover,
.nav-toggle[aria-expanded="true"] {
  color: var(--color-gold);
  border-color: var(--color-gold);
  background: rgba(255, 201, 56, .08);
}

.nav-toggle-bar {
  display: block;
  width: 1.25rem;
  height: 2px;
  margin: 3px auto;
  background: currentColor;
  border-radius: 1px;
  transition: transform .2s ease, opacity .2s ease;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(1) {
  transform: translateY(5px) 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(-5px) rotate(-45deg);
}

/* ===== Directory panel ===== */
.directory-panel {
  position: fixed;
  top: 5.5rem;
  right: clamp(.75rem, 3vw, 2rem);
  width: min(30rem, calc(100vw - 2rem));
  max-height: calc(100vh - 7rem);
  overflow: auto;
  z-index: 200;
  padding: 1.5rem;
  background: rgba(9, 13, 26, .96);
  border: 1px solid var(--color-line);
  border-left: 3px solid var(--color-gold);
  border-radius: 1.5rem;
  box-shadow: 0 2rem 4rem rgba(0, 0, 0, .5);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
}

.directory-panel[data-open] {
  animation: directory-in .2s ease-out;
}

@keyframes directory-in {
  from {
    opacity: 0;
    transform: translateY(-.5rem);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.directory-heading {
  display: flex;
  align-items: center;
  gap: .75rem;
  margin: 0;
  font-family: var(--font-title);
  font-size: 1.25rem;
  font-weight: 900;
  letter-spacing: .08em;
  color: var(--color-white);
}

.directory-heading::before {
  content: "";
  width: 2rem;
  height: 2px;
  background: var(--color-gold);
}

.directory-list {
  list-style: none;
  margin: 1.25rem 0 0;
  padding: 1.25rem 0 0;
  border-top: 1px solid var(--color-line);
  display: grid;
  gap: .5rem;
}

.directory-list a {
  display: grid;
  grid-template-columns: 2rem 1fr auto;
  gap: .5rem;
  align-items: baseline;
  padding: .5rem .25rem;
  border-bottom: 1px solid rgba(31, 58, 95, .35);
  color: var(--color-muted);
  text-decoration: none;
  transition: padding-left .2s ease, color .2s ease;
}

.directory-list a:hover {
  padding-left: .5rem;
  color: var(--color-white);
}

.directory-index {
  font-family: var(--font-number);
  font-size: .75rem;
  color: var(--color-gold);
}

.directory-name {
  color: var(--color-white);
  font-weight: 500;
}

.directory-list a:hover .directory-name {
  color: var(--color-gold);
}

.directory-note {
  font-size: .75rem;
  letter-spacing: .05em;
  color: var(--color-muted);
}

/* ===== Footer ===== */
.site-footer {
  position: relative;
  isolation: isolate;
  margin-top: 4rem;
  background: linear-gradient(180deg, var(--color-bg) 0%, var(--color-bg-deep) 45%);
  border-top: 1px solid var(--color-line);
  color: var(--color-muted);
  font-size: .875rem;
}

.site-footer::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  z-index: 0;
  height: .25rem;
  background: repeating-linear-gradient(90deg, var(--color-gold) 0 8px, transparent 8px 16px, var(--color-red) 16px 20px, transparent 20px 28px);
  opacity: .55;
}

.footer-inner,
.footer-bottom {
  position: relative;
  z-index: 1;
}

.footer-inner {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1.2fr;
  gap: 2rem;
  max-width: var(--container);
  margin: 0 auto;
  padding: 3rem clamp(1rem, 3vw, 2rem) 2rem;
}

.footer-brand {
  display: grid;
  align-content: start;
  gap: 1rem;
}

.footer-logo {
  display: inline-flex;
  align-items: center;
  gap: .75rem;
  text-decoration: none;
  color: var(--color-white);
}

.footer-logo-mark {
  display: inline-block;
  font-family: var(--font-title);
  font-size: 2rem;
  font-weight: 900;
  line-height: 1;
  padding: .2rem .6rem;
  color: var(--color-gold);
  border: 1px solid var(--color-line);
  transform: skewX(-8deg);
}

.footer-logo-name {
  font-family: var(--font-title);
  font-size: 1rem;
  letter-spacing: .1em;
  color: var(--color-white);
}

.footer-slogan {
  max-width: 26rem;
  line-height: 1.8;
  color: var(--color-muted);
}

.footer-heading {
  margin: 0 0 1rem;
  font-size: .75rem;
  letter-spacing: .2em;
  text-transform: uppercase;
  line-height: 1.4;
  color: var(--color-gold);
  padding-left: .75rem;
  border-left: 2px solid var(--color-gold);
}

.footer-links {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: .4rem;
}

.footer-links a {
  display: inline-block;
  color: var(--color-muted);
  text-decoration: none;
  padding: .15rem 0;
  transition: color .2s ease, padding-left .2s ease;
}

.footer-links a:hover {
  color: var(--color-gold);
  padding-left: .35rem;
}

.footer-legal {
  display: grid;
  align-content: start;
  gap: 1rem;
}

.footer-legal .footer-links {
  gap: .25rem;
}

.footer-contact {
  line-height: 1.8;
  color: var(--color-muted);
  margin: 0;
}

.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: .5rem 1.5rem;
  max-width: var(--container);
  margin: 0 auto;
  padding: 1.25rem clamp(1rem, 3vw, 2rem);
  border-top: 1px solid var(--color-line);
}

.footer-bottom p {
  margin: 0;
}

.footer-copy,
.footer-icp {
  font-family: var(--font-number);
  font-size: .8125rem;
}

.footer-declare {
  font-size: .75rem;
  color: var(--color-muted);
  letter-spacing: .03em;
}

.footer-gold-line {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 1;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--color-gold) 20%, var(--color-red) 80%, transparent);
  pointer-events: none;
}

/* ===== A11y readable ===== */
html.a11y-readable {
  font-size: 112.5%;
}

html.a11y-readable :focus-visible {
  outline-width: 3px;
}

/* ===== Responsive ===== */
@media (max-width: 60rem) {
  .nav-shell {
    border-radius: 1.75rem;
  }

  .brand-sub {
    display: none;
  }

  .nav-main {
    order: 3;
    flex: 1 0 100%;
    display: none;
    padding-top: .5rem;
    margin-top: .25rem;
    border-top: 1px solid var(--color-line);
  }

  .nav-main[data-open] {
    display: block;
  }

  .nav-list {
    flex-direction: column;
    gap: 0;
  }

  .nav-link {
    display: block;
    width: 100%;
    padding: .875rem 1rem;
    border-bottom: 1px solid rgba(31, 58, 95, .5);
  }

  .nav-link::after {
    display: none;
  }

  .nav-link[aria-current="page"] {
    color: var(--color-gold);
    background: rgba(255, 201, 56, .06);
  }

  .nav-actions {
    margin-left: auto;
  }

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

  .icon-btn {
    width: 2.5rem;
    height: 2.5rem;
    padding: 0;
    justify-content: center;
  }

  .icon-btn-label {
    display: none;
  }

  .directory-panel {
    right: .5rem;
    width: calc(100vw - 1rem);
    top: 5rem;
  }

  .footer-inner {
    grid-template-columns: 1fr 1fr;
    row-gap: 2.5rem;
  }

  .footer-brand {
    grid-column: 1 / -1;
  }
}

@media (max-width: 40rem) {
  .footer-inner {
    grid-template-columns: 1fr;
  }

  .footer-brand {
    grid-column: auto;
  }

  .footer-bottom {
    justify-content: center;
    text-align: center;
  }

  .footer-declare {
    flex-basis: 100%;
  }

  .nav-shell {
    gap: .5rem;
    padding: .4rem .75rem;
  }

  .brand-mark {
    font-size: 1.4rem;
    padding-right: .5rem;
  }

  .directory-panel {
    padding: 1.25rem;
  }
}

/* ===== Reduced motion ===== */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .01ms !important;
  }
}