/* ===== 全站变量 ===== */
:root {
  --color-primary: #0A1F44;
  --color-primary-light: #1A3A6B;
  --color-primary-dark: #061430;
  --color-accent: #FF6B00;
  --color-accent-gold: #FFD700;
  --color-surface: #0D2A52;
  --color-text: #F0F4F8;
  --color-text-muted: #A0B2C6;
  --color-border: rgba(255, 255, 255, 0.1);
  --color-success: #00C853;
  --color-warning: #FFD700;
  --font-heading: "Noto Serif SC", "Playfair Display", "Source Han Serif SC", "Songti SC", serif;
  --font-body: "Noto Sans SC", "Inter", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-data: "IBM Plex Mono", "JetBrains Mono", "SF Mono", "Consolas", monospace;
  --header-height: 4.5rem;
  --content-max: 1200px;
  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 1.5rem;
  --space-lg: 2.5rem;
  --space-xl: 4rem;
  --transition: 0.25s ease;
}

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

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

body {
  background: var(--color-primary);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
}

main {
  display: block;
  padding-top: calc(var(--header-height) + 1rem);
}

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

ul[class],
ol[class] {
  list-style: none;
}

a {
  color: inherit;
}

button {
  font: inherit;
  color: inherit;
}

h1,
h2,
h3,
h4,
h5 {
  font-family: var(--font-heading);
  font-weight: 900;
  line-height: 1.25;
  color: #fff;
  text-wrap: balance;
}

p {
  text-wrap: pretty;
}

/* ===== 可访问性 ===== */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
}

.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: fixed;
  top: -100px;
  left: 1rem;
  z-index: 2000;
  background: var(--color-accent);
  color: var(--color-primary-dark);
  padding: 0.625rem 1.25rem;
  font-weight: 700;
  text-decoration: none;
  transition: top var(--transition);
}
.skip-link:focus {
  top: 1rem;
}

/* ===== 通用布局 ===== */
.layout-container {
  width: min(var(--content-max), calc(100% - 2.5rem));
  margin-inline: auto;
}

.section {
  padding-block: clamp(3.5rem, 8vw, 6.5rem);
  position: relative;
}

.section--alt {
  background: var(--color-surface);
}

.layout-split {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: clamp(1.5rem, 4vw, 4rem);
  align-items: start;
}

/* ===== 章节标题 ===== */
.section-heading {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 0.75rem 1rem;
  margin-bottom: clamp(1.5rem, 3vw, 2.5rem);
}

.section-heading__index {
  font-family: var(--font-data);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-accent);
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.section-heading__title {
  font-family: var(--font-heading);
  font-size: clamp(1.75rem, 3.5vw, 2.75rem);
  font-weight: 900;
  line-height: 1.2;
  color: #fff;
}

.section-heading__lead {
  flex-basis: 100%;
  color: var(--color-text-muted);
  max-width: 50ch;
}

/* ===== 站点头部 ===== */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: transparent;
  border-bottom: 1px solid transparent;
  transition: background var(--transition), border-color var(--transition), box-shadow var(--transition), backdrop-filter var(--transition);
}

.site-header[data-scrolled] {
  background: rgba(10, 31, 68, 0.94);
  border-bottom-color: var(--color-border);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.2);
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-height);
  max-width: var(--content-max);
  margin-inline: auto;
  padding-inline: var(--space-md);
  position: relative;
}

.site-header__brand {
  display: inline-flex;
  align-items: baseline;
  gap: 0.5rem;
  text-decoration: none;
  color: #fff;
  flex-shrink: 0;
}

.site-header__brand-name {
  font-family: var(--font-heading);
  font-size: 1.375rem;
  font-weight: 900;
  letter-spacing: 0.06em;
  line-height: 1;
}

.site-header__brand-version {
  font-family: var(--font-data);
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--color-accent);
  background: var(--color-primary-dark);
  padding: 0.25rem 0.5rem;
  line-height: 1;
  clip-path: polygon(0 0, 100% 0, calc(100% - 6px) 100%, 0 100%);
}

.site-header__nav-list {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  list-style: none;
}

.site-header__nav-link {
  position: relative;
  display: block;
  padding: 0.5rem 0.875rem;
  color: rgba(240, 244, 248, 0.85);
  font-size: 0.9375rem;
  font-weight: 500;
  text-decoration: none;
  letter-spacing: 0.02em;
  transition: color var(--transition);
}

.site-header__nav-link:hover {
  color: #fff;
}

.site-header__nav-link[aria-current="page"] {
  color: var(--color-accent);
  font-weight: 700;
}

.site-header__nav-link[aria-current="page"]::after {
  content: "";
  position: absolute;
  left: 0.875rem;
  right: 0.875rem;
  bottom: 0.125rem;
  height: 2px;
  background: var(--color-accent);
  transform: scaleX(1);
  transform-origin: left;
}

.site-header__toggle {
  display: none;
  width: 44px;
  height: 44px;
  padding: 11px;
  border: 0;
  background: transparent;
  cursor: pointer;
  flex-direction: column;
  justify-content: center;
  gap: 4px;
}

.site-header__toggle-bar {
  display: block;
  height: 2px;
  background: #fff;
  transition: transform 0.3s ease, opacity 0.3s ease;
}

.site-header__toggle.is-active .site-header__toggle-bar:nth-child(1) {
  transform: translateY(6px) rotate(45deg);
}

.site-header__toggle.is-active .site-header__toggle-bar:nth-child(2) {
  opacity: 0;
}

.site-header__toggle.is-active .site-header__toggle-bar:nth-child(3) {
  transform: translateY(-6px) rotate(-45deg);
}

.site-header__progress {
  position: absolute;
  left: 0;
  bottom: 0;
  height: 3px;
  width: 100%;
  background: linear-gradient(90deg, var(--color-accent), var(--color-accent-gold));
  transform: scaleX(0);
  transform-origin: 0 50%;
  transition: transform 0.1s linear;
  pointer-events: none;
}

/* ===== 站点页脚 ===== */
.site-footer {
  background: linear-gradient(180deg, var(--color-primary) 0%, var(--color-primary-dark) 45%);
  border-top: 1px solid var(--color-border);
  padding-top: clamp(3rem, 6vw, 5rem);
}

.site-footer__grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1.4fr;
  gap: clamp(1.5rem, 3vw, 3rem);
  padding-bottom: clamp(2.5rem, 5vw, 4rem);
}

.site-footer__brand {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.site-footer__logo {
  display: inline-flex;
  align-items: baseline;
  gap: 0.5rem;
  text-decoration: none;
  color: #fff;
  width: fit-content;
}

.site-footer__logo-name {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 900;
  letter-spacing: 0.06em;
}

.site-footer__logo-version {
  font-family: var(--font-data);
  font-size: 0.8125rem;
  font-weight: 700;
  color: var(--color-accent);
  background: var(--color-primary-light);
  padding: 0.25rem 0.5rem;
  clip-path: polygon(0 0, 100% 0, calc(100% - 6px) 100%, 0 100%);
}

.site-footer__tagline {
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  max-width: 34em;
  line-height: 1.7;
}

.site-footer__heading {
  font-family: var(--font-heading);
  font-size: 1rem;
  font-weight: 700;
  margin: 0 0 1rem;
  color: #fff;
  letter-spacing: 0.08em;
}

.site-footer__links,
.site-footer__contact-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.625rem;
}

.site-footer__links a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.9375rem;
  transition: color 0.2s ease, padding-left 0.2s ease;
}

.site-footer__links a:hover {
  color: var(--color-accent);
  padding-left: 0.25rem;
}

.site-footer__contact-list {
  gap: 0.75rem;
}

.site-footer__contact-item {
  display: flex;
  flex-direction: column;
  gap: 0.125rem;
}

.site-footer__contact-label {
  font-size: 0.75rem;
  color: var(--color-accent);
  letter-spacing: 0.1em;
  font-weight: 600;
}

.site-footer__contact-value {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  line-height: 1.5;
}

.site-footer__bottom {
  border-top: 1px solid var(--color-border);
  padding: 1.25rem 0;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.site-footer__note {
  letter-spacing: 0.04em;
}

/* ===== 按钮 ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.625rem;
  padding: 0.8125rem 1.75rem;
  background: var(--color-accent);
  color: var(--color-primary-dark);
  border: 2px solid var(--color-accent);
  font-family: var(--font-body);
  font-size: 0.9375rem;
  font-weight: 700;
  line-height: 1;
  text-decoration: none;
  cursor: pointer;
  position: relative;
  clip-path: polygon(0 0, calc(100% - 12px) 0, 100% 12px, 100% 100%, 0 100%);
  transition: background 0.25s ease, color 0.25s ease, border-color 0.25s ease, transform 0.25s ease;
}

.btn::after {
  content: "→";
  transition: transform 0.2s ease;
}

.btn:hover::after {
  transform: translateX(4px);
}

.btn:hover {
  background: transparent;
  color: var(--color-accent);
  border-color: var(--color-accent);
}

.btn:active {
  transform: translateY(1px);
}

.btn--ghost {
  background: transparent;
  color: #fff;
  border-color: rgba(255, 255, 255, 0.3);
}

.btn--ghost:hover {
  background: rgba(255, 107, 0, 0.06);
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.btn--sm {
  padding: 0.5625rem 1.125rem;
  font-size: 0.875rem;
}

/* ===== 面包屑 ===== */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
  padding: calc(var(--header-height) + 1.5rem) 0 1rem;
  font-family: var(--font-data);
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.breadcrumb a {
  color: var(--color-text-muted);
  text-decoration: none;
  transition: color 0.2s ease;
}

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

.breadcrumb__sep {
  color: var(--color-accent);
  margin: 0 0.25rem;
}

.breadcrumb__current {
  color: #fff;
}

/* ===== 标签 ===== */
.tag {
  display: inline-flex;
  align-items: center;
  padding: 0.375rem 0.75rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  color: var(--color-text-muted);
  font-family: var(--font-data);
  font-size: 0.75rem;
  letter-spacing: 0.05em;
  text-decoration: none;
  transition: color 0.2s ease, border-color 0.2s ease;
}

.tag:hover {
  color: var(--color-accent);
  border-color: var(--color-accent);
}

.tag--gold {
  color: var(--color-accent-gold);
  border-color: rgba(255, 215, 0, 0.4);
}

/* ===== 数据展示 ===== */
.data-display {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.data-display__value {
  font-family: var(--font-data);
  font-size: clamp(2.75rem, 6vw, 4.5rem);
  font-weight: 700;
  line-height: 0.95;
  color: #fff;
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.03em;
}

.data-display__value--accent {
  color: var(--color-accent);
}

.data-display__value--gold {
  color: var(--color-accent-gold);
}

.data-display__label {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  letter-spacing: 0.08em;
}

/* ===== 数据表格 ===== */
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--font-body);
  font-size: 0.9375rem;
}

.data-table th {
  font-family: var(--font-data);
  font-size: 0.8125rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
  text-align: left;
  padding: 0.875rem 1rem;
  border-bottom: 1px solid var(--color-border);
}

.data-table td {
  padding: 1rem;
  border-bottom: 1px solid var(--color-border);
  color: var(--color-text);
  font-variant-numeric: tabular-nums;
}

.data-table tr:last-child td {
  border-bottom: 0;
}

.data-table tbody tr:hover {
  background: rgba(255, 255, 255, 0.03);
}

/* ===== 图片容器 ===== */
.img-frame {
  position: relative;
  overflow: hidden;
  background: linear-gradient(135deg, var(--color-primary-light) 0%, var(--color-primary-dark) 100%);
  border: 1px solid var(--color-border);
  aspect-ratio: 16 / 10;
}

.img-frame::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    linear-gradient(rgba(255, 255, 255, 0.04) 1px, transparent 1px) 0 0 / 100% 24px,
    linear-gradient(90deg, rgba(255, 255, 255, 0.04) 1px, transparent 1px) 0 0 / 24px 100%;
  pointer-events: none;
  z-index: 0;
}

.img-frame--portrait {
  aspect-ratio: 4 / 5;
}

.img-frame--wide {
  aspect-ratio: 21 / 9;
}

.img-frame img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  z-index: 1;
  transition: transform 0.45s ease;
}

.img-frame:hover img {
  transform: scale(1.04);
}

.img-frame__placeholder {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  color: var(--color-text-muted);
  font-family: var(--font-data);
  font-size: 0.875rem;
  letter-spacing: 0.08em;
  z-index: 1;
}

/* ===== 装饰与分隔 ===== */
.divider {
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--color-border) 30%, var(--color-border) 70%, transparent);
  border: 0;
}

.speed-lines {
  height: 3px;
  background: repeating-linear-gradient(
    90deg,
    var(--color-accent) 0px,
    var(--color-accent) 48px,
    transparent 48px,
    transparent 96px
  );
  opacity: 0.8;
}

.speed-lines--gold {
  background: repeating-linear-gradient(
    90deg,
    var(--color-accent-gold) 0px,
    var(--color-accent-gold) 32px,
    transparent 32px,
    transparent 72px
  );
}

/* ===== 专题研究板 ===== */
.study-board {
  background: var(--color-surface);
  border-left: 3px solid var(--color-accent);
  padding: clamp(1.5rem, 3vw, 2.5rem);
  position: relative;
}

.study-board__section-title {
  font-family: var(--font-data);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--color-accent);
  margin-bottom: 0.75rem;
}

.study-board__title {
  font-family: var(--font-heading);
  font-size: 1.375rem;
  font-weight: 900;
  color: #fff;
  margin-bottom: 0.875rem;
}

.study-board__summary {
  color: var(--color-text-muted);
  margin-bottom: 1.25rem;
}

.study-board__evidence {
  border-top: 1px solid var(--color-border);
  padding-top: 1.25rem;
  margin-top: 1.25rem;
}

.study-board__terms {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1rem;
}

.study-board__extend {
  margin-top: 1.25rem;
  padding-top: 1.25rem;
  border-top: 1px dashed var(--color-border);
}

/* ===== 滚动显现 ===== */
html.js [data-reveal] {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s cubic-bezier(0.2, 0.6, 0.2, 1), transform 0.6s cubic-bezier(0.2, 0.6, 0.2, 1);
  transition-delay: var(--reveal-delay, 0s);
}

html.js [data-reveal][data-revealed] {
  opacity: 1;
  transform: none;
}

/* ===== 响应式 ===== */
@media (max-width: 920px) {
  .layout-split {
    grid-template-columns: 1fr;
  }

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

@media (max-width: 860px) {
  .site-header__toggle {
    display: inline-flex;
  }

  .site-header__nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background: var(--color-primary-dark);
    border-bottom: 1px solid var(--color-border);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.3);
    padding: 1.25rem;
    transform: translateY(-12px);
    opacity: 0;
    pointer-events: none;
    transition: transform 0.3s ease, opacity 0.3s ease;
  }

  .site-header__nav[data-open] {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }

  .site-header__nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
  }

  .site-header__nav-link {
    padding: 1rem 1.25rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.06);
    font-size: 1rem;
  }

  .site-header__nav-link[aria-current="page"] {
    background: rgba(255, 107, 0, 0.08);
  }

  .site-header__nav-link[aria-current="page"]::after {
    left: 1.25rem;
    right: auto;
    width: 3px;
    height: 55%;
    top: 50%;
    bottom: auto;
    transform: translateY(-50%);
  }
}

@media (max-width: 640px) {
  :root {
    --header-height: 3.75rem;
  }

  .layout-container {
    width: min(var(--content-max), calc(100% - 2rem));
  }

  .site-header__brand-name {
    font-size: 1.125rem;
  }

  .site-header__brand-version {
    font-size: 0.6875rem;
  }

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

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

  .btn {
    width: 100%;
  }
}

/* ===== 减少动画偏好 ===== */
@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;
  }

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