:root {
  --container: 1280px;
  --gutter: clamp(1rem, 4vw, 3rem);
  --topbar-offset: 68px;
  --paper: #F5F0E8;
  --paper-rgb: 245, 240, 232;
  --ink: #1E1A24;
  --ink-rgb: 30, 26, 36;
  --navy: #0B3D91;
  --navy-rgb: 11, 61, 145;
  --lime: #39FF14;
  --orange: #FF6B00;
  --line: #D8D2C4;
  --gray: #6B6B6B;
  --shadow: rgba(0, 0, 0, 0.08);
  --font-display: "Archivo Black", "HarmonyOS Sans SC", "Source Han Sans SC", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-body: "Inter", "HarmonyOS Sans SC", "Source Han Sans SC", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--topbar-offset) + 12px);
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

main {
  flex: 1;
  width: 100%;
}

main:focus {
  outline: none;
}

h1,
h2,
h3 {
  font-family: var(--font-display);
  line-height: 1.15;
  color: var(--ink);
}

a {
  color: var(--navy);
  text-underline-offset: 2px;
}

button {
  font: inherit;
  color: inherit;
  background: none;
  border: none;
  cursor: pointer;
}

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

::selection {
  background: var(--lime);
  color: var(--ink);
}

:focus-visible {
  outline: 3px solid var(--navy);
  outline-offset: 2px;
  border-radius: 2px;
}

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

.container--narrow {
  max-width: 880px;
}

.skip-link {
  position: fixed;
  top: -120px;
  left: 16px;
  z-index: 100;
  display: inline-flex;
  align-items: center;
  padding: 10px 18px;
  background: var(--navy);
  color: #fff;
  font-size: 14px;
  font-weight: 700;
  text-decoration: none;
  border-radius: 4px;
  border: 1px solid var(--lime);
  transition: top 0.25s var(--ease);
}

.skip-link:focus-visible {
  top: 12px;
  color: #fff;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--paper);
  border-bottom: 1px solid var(--line);
  transition: box-shadow 0.25s var(--ease), background 0.25s var(--ease);
}

.site-header[data-scrolled="true"] {
  background: rgba(var(--paper-rgb), 0.86);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 6px 24px var(--shadow);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  max-width: var(--container);
  margin-inline: auto;
  padding: 12px var(--gutter);
  transition: padding 0.25s var(--ease);
}

.site-header[data-scrolled="true"] .header-container {
  padding-top: 6px;
  padding-bottom: 6px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-right: auto;
  min-width: 0;
  color: var(--ink);
  text-decoration: none;
}

.brand-mark {
  position: relative;
  flex: 0 0 auto;
  width: 36px;
  height: 28px;
  border: 2px solid var(--ink);
  border-radius: 3px;
  transform: skewX(-12deg);
  background: var(--paper);
}

.brand-mark::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, transparent 42%, var(--lime) 43%, var(--lime) 57%, transparent 58%),
    linear-gradient(90deg, transparent 38%, var(--navy) 39%, var(--navy) 61%, transparent 62%);
  opacity: 0.9;
}

.brand-mark::after {
  content: "";
  position: absolute;
  left: 5px;
  right: 5px;
  top: 50%;
  height: 1px;
  background: var(--orange);
  transform: translateY(-50%);
}

.brand-name {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: 0.02em;
  white-space: nowrap;
  color: var(--ink);
}

.brand-slogan {
  padding-left: 12px;
  border-left: 1px solid var(--line);
  font-size: 11px;
  font-weight: 300;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--gray);
  white-space: nowrap;
}

.main-nav {
  display: flex;
  align-items: center;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 2px;
  list-style: none;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  padding: 8px 14px;
  border: 1px solid transparent;
  border-radius: 999px;
  color: var(--ink);
  font-size: 14px;
  font-weight: 600;
  line-height: 1.2;
  text-decoration: none;
  transition: background 0.2s var(--ease), color 0.2s var(--ease), border-color 0.2s var(--ease), transform 0.2s var(--ease);
}

.nav-link:hover {
  background: rgba(var(--navy-rgb), 0.05);
  border-color: var(--navy);
  color: var(--navy);
}

.nav-link[aria-current="page"] {
  background: var(--navy);
  border-color: var(--navy);
  color: #fff;
}

.nav-badge {
  display: inline-block;
  width: 6px;
  height: 6px;
  margin-left: 6px;
  border-radius: 999px;
  background: currentColor;
  vertical-align: 2px;
}

.nav-badge--hot {
  background: var(--orange);
}

.nav-toggle {
  display: none;
  position: relative;
  z-index: 63;
  width: 42px;
  height: 42px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--paper);
  transition: border-color 0.2s var(--ease), background 0.2s var(--ease);
}

.nav-toggle:hover {
  border-color: var(--ink);
  background: #fff;
}

.nav-toggle-line {
  display: block;
  width: 18px;
  height: 2px;
  margin: 4px auto;
  background: var(--ink);
  border-radius: 999px;
  transition: transform 0.25s var(--ease), opacity 0.2s var(--ease);
}

.nav-toggle[aria-expanded="true"] .nav-toggle-line:nth-child(1) {
  transform: translateY(6px) 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(-6px) rotate(-45deg);
}

.nav-scrim {
  position: fixed;
  inset: 0;
  z-index: 61;
  background: rgba(var(--ink-rgb), 0.55);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s var(--ease);
}

.nav-scrim[data-open="true"] {
  opacity: 1;
  pointer-events: auto;
}

.back-top {
  position: fixed;
  right: 20px;
  bottom: 20px;
  z-index: 70;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--paper);
  box-shadow: 0 8px 20px var(--shadow);
  font-size: 18px;
  line-height: 1;
  color: var(--ink);
  transition: opacity 0.25s var(--ease), transform 0.25s var(--ease), border-color 0.2s var(--ease), color 0.2s var(--ease);
}

.back-top:hover {
  border-color: var(--navy);
  color: var(--navy);
}

.back-top[hidden] {
  display: flex;
  opacity: 0;
  transform: translateY(10px);
  pointer-events: none;
}

.page-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -1px;
  height: 3px;
  z-index: 55;
  background: transparent;
  overflow: hidden;
}

.page-progress-fill {
  display: block;
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--navy) 0%, var(--lime) 60%, var(--orange) 100%);
}

.site-footer {
  position: relative;
  margin-top: auto;
  background: var(--ink);
  color: rgba(var(--paper-rgb), 0.78);
  border-top: 3px solid var(--navy);
  overflow: hidden;
}

.site-footer::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 6px;
  background: linear-gradient(90deg, transparent 0%, transparent 22%, var(--orange) 22%, var(--orange) 36%, transparent 36%);
  opacity: 0.8;
  pointer-events: none;
}

.footer-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.6fr) minmax(0, 1fr) minmax(0, 1fr) minmax(0, 1.2fr);
  gap: clamp(1.5rem, 4vw, 3rem);
  padding: 48px 0 40px;
}

.footer-brand {
  min-width: 0;
}

.footer-brand-name {
  font-family: var(--font-display);
  font-size: 26px;
  line-height: 1.1;
  font-weight: 700;
  color: var(--paper);
  letter-spacing: 0.03em;
}

.footer-trust {
  margin-top: 14px;
  max-width: 320px;
  font-size: 14px;
  line-height: 1.7;
  color: rgba(var(--paper-rgb), 0.62);
}

.footer-slogan {
  margin-top: 14px;
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--lime);
}

.footer-col {
  min-width: 0;
}

.footer-title {
  font-family: var(--font-display);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--paper);
  border-bottom: 1px solid rgba(var(--paper-rgb), 0.12);
  padding-bottom: 8px;
  margin-bottom: 16px;
}

.footer-list {
  display: grid;
  gap: 8px;
  list-style: none;
}

.footer-list a {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: rgba(var(--paper-rgb), 0.72);
  font-size: 14px;
  text-decoration: none;
  transition: color 0.2s var(--ease), gap 0.2s var(--ease);
}

.footer-list a::before {
  content: "";
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: var(--navy);
  transition: background 0.2s var(--ease), transform 0.2s var(--ease);
}

.footer-list a:hover {
  color: var(--lime);
  gap: 10px;
}

.footer-list a:hover::before {
  background: var(--orange);
  transform: scale(1.25);
}

.footer-info {
  margin: 0 0 10px;
  font-size: 14px;
  line-height: 1.6;
  color: rgba(var(--paper-rgb), 0.78);
}

.footer-note {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px solid rgba(var(--paper-rgb), 0.12);
  font-size: 12px;
  line-height: 1.6;
  color: rgba(var(--paper-rgb), 0.52);
}

.footer-bottom {
  border-top: 1px solid rgba(var(--paper-rgb), 0.12);
  padding: 16px 0;
}

.footer-bottom-inner {
  display: flex;
  justify-content: space-between;
  gap: 8px 20px;
  flex-wrap: wrap;
  font-size: 13px;
  color: rgba(var(--paper-rgb), 0.5);
}

.grid {
  display: grid;
  gap: clamp(1rem, 2vw, 1.5rem);
}

.grid--2 {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.grid--3 {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.grid--4 {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.card {
  background: rgba(255, 255, 255, 0.5);
  border: 1px solid var(--line);
  border-radius: 6px;
  overflow: hidden;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.04);
  transition: transform 0.25s var(--ease), box-shadow 0.25s var(--ease), border-color 0.2s var(--ease);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 10px 28px var(--shadow);
  border-color: var(--navy);
}

.card-body {
  padding: 20px 22px;
}

.card-title {
  font-family: var(--font-display);
  font-size: 18px;
  font-weight: 600;
  line-height: 1.3;
  color: var(--ink);
}

.card-meta {
  margin-top: 6px;
  font-size: 12px;
  color: var(--gray);
}

.section-head {
  display: grid;
  gap: 8px;
  margin-bottom: 28px;
}

.index-label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-display);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--navy);
}

.index-label::before {
  content: "";
  width: 22px;
  height: 2px;
  background: var(--lime);
}

.section-title {
  font-family: var(--font-display);
  font-size: clamp(28px, 5vw, 44px);
  font-weight: 900;
  line-height: 1.08;
  letter-spacing: -0.04em;
  color: var(--ink);
  margin: 0;
}

.section-desc {
  font-size: 15px;
  line-height: 1.65;
  color: var(--gray);
  max-width: 60ch;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  border-radius: 999px;
  background: var(--navy);
  color: #fff;
  font-size: 12px;
  font-weight: 600;
  line-height: 1.4;
  white-space: nowrap;
}

.badge--hot {
  background: var(--orange);
  color: var(--ink);
}

.badge--lime {
  background: var(--lime);
  color: var(--ink);
}

.band {
  padding: clamp(2.5rem, 6vw, 5rem) 0;
}

.band--dark {
  background: var(--ink);
  color: rgba(var(--paper-rgb), 0.82);
}

.band--dark .section-title {
  color: var(--paper);
}

.band--dark .index-label {
  color: var(--lime);
}

.btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 20px;
  border: 1px solid var(--ink);
  border-radius: 4px;
  background: transparent;
  color: var(--ink);
  font-size: 14px;
  font-weight: 600;
  line-height: 1.2;
  text-decoration: none;
  overflow: hidden;
  transition: color 0.2s var(--ease), background 0.2s var(--ease), border-color 0.2s var(--ease), transform 0.2s var(--ease);
}

.btn::after {
  content: "";
  position: absolute;
  top: 0;
  left: -70%;
  width: 45%;
  height: 100%;
  background: linear-gradient(105deg, transparent, rgba(255, 255, 255, 0.4), transparent);
  transform: skewX(-20deg);
  transition: left 0.3s var(--ease);
}

.btn:hover::after {
  left: 130%;
}

.btn:hover {
  transform: translateY(-1px);
  border-color: var(--navy);
}

.btn--lime {
  background: var(--lime);
  border-color: var(--lime);
  color: var(--ink);
}

.btn--lime:hover {
  background: #5cff3b;
  border-color: var(--lime);
  color: var(--ink);
}

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

.btn--navy:hover {
  background: var(--ink);
  border-color: var(--ink);
  color: var(--paper);
}

.btn--ghost {
  background: transparent;
  border-color: var(--line);
  color: var(--ink);
}

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

.breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
  margin-bottom: 24px;
  font-size: 13px;
}

.breadcrumbs__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
  list-style: none;
}

.breadcrumbs__item {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.breadcrumbs__item + .breadcrumbs__item::before {
  content: "/";
  color: var(--line);
}

.breadcrumbs a {
  color: var(--navy);
  text-decoration: none;
}

.breadcrumbs a:hover {
  text-decoration: underline;
}

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

.chapter-nav {
  position: sticky;
  top: calc(var(--topbar-offset) + 8px);
  z-index: 20;
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  width: fit-content;
  max-width: 100%;
  padding: 8px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: rgba(var(--paper-rgb), 0.92);
  box-shadow: 0 6px 20px var(--shadow);
}

.chapter-link {
  display: inline-flex;
  align-items: center;
  padding: 7px 14px;
  border: 1px solid transparent;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 600;
  color: var(--ink);
  text-decoration: none;
  transition: background 0.2s var(--ease), color 0.2s var(--ease), border-color 0.2s var(--ease);
}

.chapter-link:hover {
  border-color: var(--navy);
  color: var(--navy);
}

.chapter-link.is-active,
.chapter-link[aria-current="true"] {
  background: var(--ink);
  border-color: var(--ink);
  color: var(--paper);
}

.media-frame {
  position: relative;
  display: block;
  overflow: hidden;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: 4px;
}

.media-frame::before {
  content: "";
  display: block;
  padding-top: 56.25%;
}

.media-frame--4-3::before {
  padding-top: 75%;
}

.media-frame--square::before {
  padding-top: 100%;
}

.media-frame > img,
.media-frame > .media-bg {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.media-bg {
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #e9e1d4, var(--paper), #ded4c2);
}

.media-bg::after {
  content: attr(data-label);
  font-size: 12px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--gray);
}

@supports not (backdrop-filter: blur(12px)) {
  .site-header[data-scrolled="true"] {
    background: var(--paper);
  }
}

@media (max-width: 1024px) {
  .grid--4 {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
  .grid--3 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  .footer-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 32px 24px;
  }
}

@media (max-width: 900px) {
  .brand-slogan {
    display: none;
  }

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

  .main-nav {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    z-index: 62;
    width: min(80vw, 320px);
    padding: 80px 24px 32px;
    background: var(--ink);
    border-left: 3px solid var(--navy);
    transform: translateX(102%);
    transition: transform 0.3s var(--ease), box-shadow 0.3s var(--ease);
  }

  .main-nav[data-open="true"] {
    transform: translateX(0);
    box-shadow: -8px 0 24px rgba(0, 0, 0, 0.25);
  }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 6px;
  }

  .nav-link {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 14px;
    border-radius: 6px;
    font-size: 16px;
    color: rgba(var(--paper-rgb), 0.88);
    border: 1px solid transparent;
  }

  .nav-link:hover {
    background: transparent;
    border-color: rgba(var(--lime), 0.4);
    color: var(--lime);
  }

  .nav-link[aria-current="page"] {
    background: var(--lime);
    border-color: var(--lime);
    color: var(--ink);
  }

  .nav-badge--hot {
    background: var(--orange);
  }

  .nav-scrim {
    display: block;
  }
}

@media (min-width: 901px) {
  .nav-scrim {
    display: none;
  }
}

@media (max-width: 680px) {
  .grid--2,
  .grid--3,
  .grid--4 {
    grid-template-columns: minmax(0, 1fr);
  }

  .footer-grid {
    grid-template-columns: minmax(0, 1fr);
    padding-top: 36px;
    padding-bottom: 32px;
  }

  .footer-brand-name {
    font-size: 22px;
  }

  .back-top {
    right: 14px;
    bottom: 14px;
    width: 40px;
    height: 40px;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  html {
    scroll-behavior: auto;
  }

  .back-top,
  .nav-scrim,
  .main-nav,
  .nav-toggle-line,
  .nav-link,
  .card,
  .btn {
    transition: none;
  }
}