:root {
  --color-surface: #fcfcfc;
  --color-surface-alt: #f4f3f3;
  --color-surface-deep: #e8e6e6;
  --color-ink: #534846;
  --color-ink-soft: #7b6d6b;
  --color-ink-muted: #877a78;
  --color-line: #dedcdb;
  --color-primary: #89706b;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #ece8e8;
  --color-accent: #dd3718;
  --color-accent-ink: #ffffff;
  --color-highlight: #f6d9d3;
  --color-focus: #da2b0b;
  --color-contrast-surface: #24201f;
  --color-contrast-ink: #e7e5e4;
  --color-contrast-line: #4f4b4a;
  --color-contrast-accent: #ea5539;
  --overlay-scrim: linear-gradient(180deg, rgba(36, 32, 31, 0.35) 0%, rgba(36, 32, 31, 0.72) 55%, rgba(36, 32, 31, 0.92) 100%);
  --font-heading: STZhongsong, "Source Han Serif SC", "Songti SC", SimSun, serif;
  --font-body: "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 9.5px;
  --text-sm: 13.5px;
  --text-base: 16px;
  --text-lg: 22.6px;
  --text-xl: 32.0px;
  --text-2xl: 45.2px;
  --text-3xl: 64.0px;
  --text-4xl: 90.4px;
  --text-display: clamp(37px, 7.6vw, 97px);
  --text-figure: clamp(31px, 5.5vw, 70px);
  --weight-heading: 370;
  --weight-body: 400;
  --leading-body: 1.84;
  --leading-heading: 1.2;
  --tracking-heading: 0.015em;
  --radius-sm: 0px;
  --radius-md: 0px;
  --radius-lg: 0px;
  --radius-pill: 0px;
  --border-thin: 1px;
  --border-thick: 1px;
  --shadow-1: none;
  --shadow-2: none;
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1160px;
  --measure: 60ch;
  --gutter: 16px;
  --section-y: 128px;
  --section-y-lg: 179px;
}

/* ============ 1. reset ============ */
*,
*::before,
*::after { box-sizing: border-box; }

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

body {
  margin: 0;
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  -webkit-font-smoothing: antialiased;
}

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

button {
  font: inherit;
  color: inherit;
  background: none;
  border: 0;
  cursor: pointer;
}

a { color: inherit; }

ul,
ol { margin: 0; padding: 0; }

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

/* ============ 2. 中文排版 ============ */
h1,
h2,
h3,
h4 {
  margin: 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-primary);
}

p { margin: 0 0 var(--space-3); }

.display {
  font-family: var(--font-heading);
  font-size: var(--text-display);
  font-weight: var(--weight-heading);
  line-height: 1.04;
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
  margin: 0;
}

.fig {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  font-weight: var(--weight-body);
  line-height: 1;
  letter-spacing: -0.01em;
  font-variant-numeric: tabular-nums;
  color: var(--color-ink);
}

.eyebrow {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.plate {
  display: block;
  margin: var(--space-2) 0 0;
  padding-left: var(--space-2);
  border-left: var(--border-thin) solid var(--color-line);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  line-height: 1.6;
  letter-spacing: 0.02em;
  color: var(--color-ink-muted);
}

.prose {
  max-width: var(--measure);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink);
}

.prose h3 {
  margin: var(--space-6) 0 var(--space-2);
  font-size: var(--text-lg);
  color: var(--color-primary);
}

.prose ul { padding-left: 1.2em; margin: 0 0 var(--space-3); }

.mono { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }
.muted { color: var(--color-ink-muted); }

/* ============ 3. 布局骨架 ============ */
.container {
  width: min(100% - var(--space-4), var(--container));
  margin-inline: auto;
}

.section { padding-block: var(--section-y); }
.section--lg { padding-block: var(--section-y-lg); }

.section--deep {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.section--deep .display,
.section--deep .chapter__title,
.section--deep h2,
.section--deep h3 { color: var(--color-contrast-ink); }

.section--deep .eyebrow,
.section--deep .plate {
  color: color-mix(in srgb, var(--color-contrast-ink) 70%, var(--color-contrast-surface));
}

.section--deep .plate { border-left-color: var(--color-contrast-line); }

.rule {
  border: 0;
  border-top: var(--border-thin) solid var(--color-line);
  margin: 0;
}

.section--deep .rule,
.site-footer .rule { border-top-color: var(--color-contrast-line); }

/* ============ 4. skip link ============ */
.skip-link {
  position: absolute;
  left: var(--space-2);
  top: -120px;
  z-index: 200;
  padding: var(--space-2) var(--space-3);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  text-decoration: none;
  transition: top 160ms ease;
}

.skip-link:focus { top: var(--space-2); }

/* ============ 5. 头部 ============ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 80;
  background-color: color-mix(in srgb, var(--color-surface) 94%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.header-bar {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: var(--space-4);
  width: min(100% - var(--space-4), var(--container));
  margin-inline: auto;
  min-height: 72px;
  padding-block: var(--space-2);
}

.brand {
  display: flex;
  flex-direction: column;
  gap: 2px;
  text-decoration: none;
}

.brand__mark {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-primary);
  white-space: nowrap;
}

.brand__sub {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

/* 赛季轴 —— 紧凑命令栏中的横向索引 */
.season-axis {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-width: 0;
}

.season-axis__label {
  flex: none;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.season-axis__list {
  display: flex;
  gap: var(--space-3);
  list-style: none;
  margin: 0;
  padding: 0 0 2px;
  overflow-x: auto;
  scrollbar-width: thin;
  scroll-behavior: smooth;
}

.season-chip {
  position: relative;
  display: inline-block;
  padding-block: 3px;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-variant-numeric: tabular-nums;
  color: var(--color-ink-soft);
  text-decoration: none;
  white-space: nowrap;
  border-bottom: var(--border-thin) solid transparent;
  transition: color 180ms ease, border-color 180ms ease;
}

.season-chip:hover {
  color: var(--color-ink);
  border-bottom-color: var(--color-line);
}

.season-chip.is-current {
  color: var(--color-ink);
  border-bottom-color: var(--color-primary);
}

.season-chip.is-current::after {
  content: "";
  position: absolute;
  left: 0;
  top: -3px;
  width: 4px;
  height: 4px;
  background-color: var(--color-accent);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  justify-self: end;
}

.header-link {
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  text-decoration: none;
  padding-bottom: 2px;
  border-bottom: var(--border-thin) solid transparent;
  transition: color 180ms ease, border-color 180ms ease;
}

.header-link:hover {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.status-hint {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
  white-space: nowrap;
}

.status-dot {
  width: 5px;
  height: 5px;
  background-color: var(--color-accent);
}

/* 按钮族 */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 9px 18px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background-color: transparent;
  color: var(--color-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  text-decoration: none;
  white-space: nowrap;
  transition: background-color 200ms ease, color 200ms ease, border-color 200ms ease;
}

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

.btn--solid:hover { background-color: color-mix(in srgb, var(--color-primary) 82%, var(--color-contrast-surface)); }

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

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

/* 移动导航开关 */
.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-1) var(--space-2);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
}

.nav-toggle__bars {
  position: relative;
  display: block;
  width: 16px;
  height: 1px;
  background-color: currentColor;
}

.nav-toggle__bars::before,
.nav-toggle__bars::after {
  content: "";
  position: absolute;
  left: 0;
  width: 16px;
  height: 1px;
  background-color: currentColor;
}

.nav-toggle__bars::before { top: -5px; }
.nav-toggle__bars::after { top: 5px; }

.nav-toggle[aria-expanded="true"] {
  background-color: var(--color-primary-soft);
  color: var(--color-primary);
  border-color: var(--color-primary);
}

/* 主导航 */
.site-nav {
  border-top: var(--border-thin) solid var(--color-line);
  background-color: var(--color-surface);
}

.site-nav__list {
  width: min(100% - var(--space-4), var(--container));
  margin: 0 auto;
  padding: var(--space-2) 0;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-6);
}

.site-nav__link {
  position: relative;
  display: inline-block;
  padding: 6px 0 6px 14px;
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  color: var(--color-ink-soft);
  text-decoration: none;
  border-bottom: var(--border-thin) solid transparent;
  transition: color 180ms ease, border-color 180ms ease;
}

.site-nav__link::after {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 4px;
  height: 4px;
  margin-top: -2px;
  background-color: var(--color-accent);
  opacity: 0;
  transition: opacity 180ms ease;
}

.site-nav__link:hover { color: var(--color-ink); }

.site-nav__link[aria-current="page"] {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.site-nav__link[aria-current="page"]::after { opacity: 1; }

/* ============ 6. 页脚 ============ */
.site-footer {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-top: var(--border-thin) solid var(--color-contrast-line);
}

.footer-grid {
  width: min(100% - var(--space-4), var(--container));
  margin-inline: auto;
  padding-block: var(--section-y);
  display: grid;
  grid-template-columns: 1.05fr 1.35fr 1fr;
}

.footer-panel {
  padding-block: var(--space-4);
  padding-right: var(--space-6);
}

.footer-panel + .footer-panel {
  padding-left: var(--space-6);
  border-left: var(--border-thin) solid var(--color-contrast-line);
}

.footer-panel__title {
  margin: 0 0 var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: var(--weight-body);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-contrast-accent);
}

.footer-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.footer-list a {
  font-size: var(--text-sm);
  color: var(--color-contrast-ink);
  text-decoration: none;
  padding-bottom: 2px;
  border-bottom: var(--border-thin) solid transparent;
  transition: border-color 180ms ease, color 180ms ease;
}

.footer-list a:hover {
  color: var(--color-primary-ink);
  border-bottom-color: var(--color-contrast-accent);
}

.footer-contact {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.footer-contact__row {
  display: grid;
  grid-template-columns: 76px minmax(0, 1fr);
  gap: var(--space-2);
  font-size: var(--text-sm);
  line-height: 1.7;
  color: color-mix(in srgb, var(--color-contrast-ink) 88%, var(--color-contrast-surface));
}

.footer-contact__key {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  padding-top: 3px;
  color: color-mix(in srgb, var(--color-contrast-ink) 58%, var(--color-contrast-surface));
}

.footer-note {
  margin: var(--space-3) 0 0;
  font-size: var(--text-sm);
  line-height: 1.7;
  color: color-mix(in srgb, var(--color-contrast-ink) 62%, var(--color-contrast-surface));
}

.footer-base { border-top: var(--border-thin) solid var(--color-contrast-line); }

.footer-base__inner {
  width: min(100% - var(--space-4), var(--container));
  margin-inline: auto;
  padding-block: var(--space-4);
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: color-mix(in srgb, var(--color-contrast-ink) 55%, var(--color-contrast-surface));
}

/* ============ 7. 通用内容组件 ============ */
.crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
  list-style: none;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}

.crumbs li + li::before {
  content: "/";
  margin-right: var(--space-2);
  color: var(--color-line);
}

.crumbs a {
  text-decoration: none;
  border-bottom: var(--border-thin) solid transparent;
}

.crumbs a:hover {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.chapter {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: var(--space-4);
  align-items: baseline;
}

.chapter__no {
  font-family: var(--font-mono);
  font-size: var(--text-4xl);
  line-height: 0.82;
  font-variant-numeric: tabular-nums;
  color: color-mix(in srgb, var(--color-primary) 42%, var(--color-surface));
}

.chapter__title {
  font-family: var(--font-heading);
  font-size: var(--text-2xl);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  color: var(--color-primary);
}

/* 图片容器基础规则（页面阶段放置图片） */
.frame {
  position: relative;
  display: block;
  overflow: hidden;
  background-color: var(--color-contrast-surface);
  border: var(--border-thin) solid var(--color-line);
}

.frame__media {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: grayscale(0.72) contrast(1.08) brightness(0.9);
}

.frame::after {
  content: "";
  position: absolute;
  inset: 0;
  background-color: color-mix(in srgb, var(--color-primary) 28%, transparent);
  mix-blend-mode: multiply;
  pointer-events: none;
}

.frame--scrim::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 1;
  background: var(--overlay-scrim);
  pointer-events: none;
}

.frame__caption {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 2;
  padding: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  line-height: 1.5;
  color: var(--color-contrast-ink);
}

.panel {
  padding: var(--space-4);
  background-color: var(--color-surface-alt);
  border: var(--border-thin) solid var(--color-line);
}

.panel--deep {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-color: var(--color-contrast-line);
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 8px;
  border: var(--border-thin) solid var(--color-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-ink-soft);
}

.tag--accent {
  color: var(--color-accent);
  border-color: color-mix(in srgb, var(--color-accent) 42%, var(--color-line));
}

.data-list {
  list-style: none;
  border-top: var(--border-thin) solid var(--color-line);
}

.data-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: var(--space-3);
  align-items: baseline;
  padding: var(--space-2) 0;
  border-bottom: var(--border-thin) solid var(--color-line);
}

.data-row__label {
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

.data-row__value {
  font-family: var(--font-mono);
  font-size: var(--text-base);
  font-variant-numeric: tabular-nums;
  text-align: right;
  color: var(--color-ink);
}

.data-row:hover { background-color: var(--color-highlight); }

.steps { list-style: none; }

.steps__item {
  display: grid;
  grid-template-columns: 56px minmax(0, 1fr);
  gap: var(--space-3);
  padding: var(--space-4) 0;
  border-top: var(--border-thin) solid var(--color-line);
}

.steps__no {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.12em;
  color: var(--color-primary);
}

.link-more {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding-bottom: 2px;
  font-size: var(--text-sm);
  color: var(--color-primary);
  text-decoration: none;
  border-bottom: var(--border-thin) solid var(--color-primary);
}

.link-more::after { content: "→"; }

.link-more:hover { color: var(--color-accent); border-bottom-color: var(--color-accent); }

/* ============ 8. 滚动显现 ============ */
[data-reveal] {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 420ms ease, transform 420ms ease;
}

[data-reveal].is-visible {
  opacity: 1;
  transform: none;
}

/* ============ 9. 响应式 ============ */
@media (max-width: 1080px) {
  .header-bar {
    grid-template-columns: auto minmax(0, 1fr) auto;
    grid-template-areas:
      "brand actions toggle"
      "axis axis axis";
    row-gap: var(--space-1);
    min-height: 0;
    padding-block: var(--space-2);
  }

  .brand { grid-area: brand; }
  .header-actions { grid-area: actions; }
  .nav-toggle { grid-area: toggle; display: inline-flex; }
  .season-axis {
    grid-area: axis;
    padding-top: var(--space-1);
    border-top: var(--border-thin) solid var(--color-line);
  }

  .status-hint,
  .header-link { display: none; }

  .site-nav { display: none; background-color: var(--color-surface-alt); }
  .site-nav[data-open] { display: block; }

  .site-nav__list {
    flex-direction: column;
    flex-wrap: nowrap;
    gap: 0;
    padding-block: 0;
  }

  .site-nav__link {
    display: block;
    padding: 14px 0 14px 14px;
    font-size: var(--text-base);
    border-bottom: var(--border-thin) solid var(--color-line);
  }

  .site-nav li:last-child .site-nav__link { border-bottom: 0; }
}

@media (max-width: 900px) {
  .footer-grid {
    grid-template-columns: 1fr;
    padding-block: var(--space-8);
  }

  .footer-panel {
    padding: var(--space-4) 0;
  }

  .footer-panel + .footer-panel {
    padding-left: 0;
    border-left: 0;
    border-top: var(--border-thin) solid var(--color-contrast-line);
  }

  .chapter { grid-template-columns: 1fr; gap: var(--space-2); }
  .chapter__no { font-size: var(--text-2xl); line-height: 1; }
}

@media (max-width: 640px) {
  .header-bar {
    grid-template-columns: minmax(0, 1fr) auto;
    grid-template-areas:
      "brand toggle"
      "axis axis";
  }

  .header-actions { display: none; }

  .section { padding-block: calc(var(--section-y) * 0.55); }
  .section--lg { padding-block: calc(var(--section-y-lg) * 0.5); }

  .chapter__title { font-size: var(--text-xl); }
  .steps__item { grid-template-columns: 40px minmax(0, 1fr); }
  .footer-contact__row { grid-template-columns: 68px minmax(0, 1fr); }
}

/* ============ 10. 无动画偏好 ============ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  [data-reveal] {
    opacity: 1;
    transform: none;
    transition: none;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}