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

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

body {
  margin: 0;
  padding-top: calc(var(--nav-top-h) + var(--nav-main-h));
  background-color: var(--night);
  background-image:
    radial-gradient(circle at 10% 6%, rgba(47, 111, 208, .20), transparent 45%),
    radial-gradient(circle at 88% 2%, rgba(255, 138, 61, .14), transparent 42%),
    radial-gradient(circle at 50% 96%, rgba(233, 185, 73, .10), transparent 54%);
  background-attachment: fixed;
  color: var(--f-white);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.85;
  letter-spacing: .01em;
}

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

h1, h2, h3, h4 {
  margin: 0;
  font-family: var(--font-title);
  font-weight: 900;
  letter-spacing: -.02em;
  line-height: 1.15;
}

p { margin: 0 0 1.4em; }

a { color: var(--gold-soft); text-decoration: none; }

ul, ol { margin: 0; padding: 0; list-style: none; }

b, strong { font-weight: 900; }

button { font: inherit; color: inherit; }

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

/* ============ 2. 变量 ============ */
:root {
  --night: #0B1230;
  --night-2: #151E48;
  --line: #2A3570;
  --gold: #E9B949;
  --gold-soft: #F6D98A;
  --flame: #FF8A3D;
  --f-blue: #2F6FD0;
  --f-white: #F4EFE2;
  --f-red: #D8383F;
  --f-green: #2FA36B;
  --f-yellow: #F2C94C;
  --wine: #7A1F2B;
  --gray: #9AA2C4;
  --f-black: #050A1A;
  --bd: 3px;
  --hard: 6px 6px 0 rgba(4, 8, 22, .92);
  --hard-gold: 6px 6px 0 rgba(233, 185, 73, .26);
  --font-title: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: "JetBrains Mono", "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --font-body: var(--font-title);
  --shell: 1200px;
  --nav-top-h: 46px;
  --nav-main-h: 62px;
  --gap-lg: 96px;
  --gap-md: 64px;
  --gap-sm: 40px;
}

/* ============ 3. 文字工具 ============ */
.mono-num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-weight: 400;
  letter-spacing: .02em;
}

.display-title {
  font-size: clamp(40px, 6.4vw, 72px);
  line-height: 1.04;
  color: var(--f-white);
  padding: 4px 20px 16px 0;
  background: linear-gradient(100deg, rgba(233, 185, 73, .20), rgba(233, 185, 73, 0) 62%);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 16px), calc(100% - 16px) 100%, 0 100%);
}

.vertical-note {
  writing-mode: vertical-rl;
  font-size: 14px;
  letter-spacing: .35em;
  color: var(--gold-soft);
  line-height: 1.4;
}

/* ============ 4. 布局工具 ============ */
.shell {
  width: 100%;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 24px;
}

.prose { max-width: 68ch; }
.prose p { margin: 0 0 1.4em; }
.prose h2 { font-size: 32px; color: var(--gold); margin: var(--gap-sm) 0 16px; }
.prose h3 { font-size: 20px; margin: 32px 0 12px; color: var(--f-white); }

.grid-12 {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: 24px;
}
.col-7 { grid-column: span 7; }
.col-5 { grid-column: span 5; }

/* ============ 5. 按钮 ============ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 18px;
  border: var(--bd) solid var(--gold);
  background: var(--night-2);
  color: var(--gold);
  font-family: var(--font-title);
  font-weight: 900;
  font-size: 15px;
  letter-spacing: .06em;
  cursor: pointer;
  box-shadow: var(--hard);
  transition: transform .12s ease, box-shadow .12s ease, background-color .12s ease, color .12s ease, border-color .12s ease;
}
.btn:hover { transform: translate(-2px, -2px); box-shadow: 8px 8px 0 rgba(4, 8, 22, .92); }
.btn:active { transform: translate(0, 0); box-shadow: 3px 3px 0 rgba(4, 8, 22, .92); }

.btn--flame {
  background: var(--flame);
  border-color: var(--flame);
  color: #1A0D04;
}
.btn--flame:hover { background: var(--gold); border-color: var(--gold); }

.btn--ghost {
  background: transparent;
  border-color: var(--line);
  color: var(--f-white);
}
.btn--ghost:hover { border-color: var(--gold); color: var(--gold); }

/* ============ 6. 头部 ============ */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
}

.skip-link {
  position: absolute;
  left: 16px;
  top: -80px;
  z-index: 200;
  padding: 10px 16px;
  background: var(--gold);
  color: #131A38;
  font-weight: 900;
  border: var(--bd) solid var(--night);
  transition: top .12s ease;
}
.skip-link:focus { top: 8px; }

.nav-top {
  background: rgba(11, 18, 48, .97);
  border-bottom: var(--bd) solid var(--line);
  backdrop-filter: blur(6px);
}
.nav-top__inner {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 24px;
  min-height: var(--nav-top-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

.brand-signature {
  margin: 0;
  display: flex;
  align-items: baseline;
  gap: 12px;
  min-width: 0;
}
.brand-name {
  font-family: var(--font-title);
  font-weight: 900;
  font-size: 16px;
  letter-spacing: .05em;
  color: var(--gold);
  white-space: nowrap;
}
.brand-tagline {
  font-size: 12px;
  letter-spacing: .2em;
  color: var(--gray);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.quick-jumps { display: flex; gap: 10px; }
.quick-jump {
  font-size: 12px;
  letter-spacing: .16em;
  padding: 3px 10px;
  border: 2px solid var(--line);
  background: var(--night-2);
  color: var(--f-white);
  white-space: nowrap;
  transition: border-color .12s ease, color .12s ease, background-color .12s ease;
}
.quick-jump:hover,
.quick-jump:focus-visible {
  border-color: var(--gold);
  color: var(--gold);
  background: #101838;
}

.utility-zone {
  display: flex;
  align-items: center;
  gap: 14px;
}
.cycle-mini {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--gray);
}
.cycle-mini__label b { color: var(--gold); }
.cycle-mini__track {
  display: block;
  width: 86px;
  height: 10px;
  border: 2px solid var(--line);
  background: #0A1029;
}
.cycle-mini__fill {
  display: block;
  height: 100%;
  width: 43%;
  background: linear-gradient(90deg, var(--f-blue), var(--gold), var(--flame));
}
.reply-hours {
  margin: 0;
  font-size: 12px;
  letter-spacing: .08em;
  color: var(--gray);
  white-space: nowrap;
}

.nav-main {
  background: var(--night-2);
  border-bottom: var(--bd) solid var(--line);
}
.nav-main__inner {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 0 24px;
  min-height: var(--nav-main-h);
  display: flex;
  align-items: center;
  gap: 18px;
}

.nav-list {
  flex: 1 1 auto;
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 7px 12px;
  border: 2px solid transparent;
  font-size: 14px;
  letter-spacing: .06em;
  color: var(--f-white);
  transition: border-color .12s ease, color .12s ease, background-color .12s ease;
}
.nav-link__strip {
  display: block;
  width: 5px;
  height: 16px;
  flex: 0 0 auto;
  background: var(--line);
  transition: height .12s ease;
}
.nav-link__label { display: block; }
.nav-link:hover,
.nav-link:focus-visible {
  border-color: var(--gold);
  color: var(--gold-soft);
}
.nav-link[aria-current="page"] {
  border-color: var(--gold);
  color: var(--gold);
  background: #131C46;
  box-shadow: var(--hard-gold);
}
.nav-link[aria-current="page"] .nav-link__strip { height: 22px; }

.nav-cta { flex: 0 0 auto; }

.nav-toggle {
  display: none;
  align-items: center;
  gap: 10px;
  padding: 8px 12px;
  border: 2px solid var(--line);
  background: #0F1738;
  color: var(--f-white);
  font-size: 12px;
  letter-spacing: .2em;
  cursor: pointer;
  transition: border-color .12s ease, color .12s ease, background-color .12s ease;
}
.nav-toggle:hover { border-color: var(--gold); color: var(--gold); }
.nav-toggle__bars { display: inline-flex; flex-direction: column; gap: 4px; width: 20px; }
.nav-toggle__bars i { display: block; height: 3px; background: currentColor; }
.nav-toggle[aria-expanded="true"] {
  border-color: var(--gold);
  color: var(--gold);
  background: #1A2352;
}

/* 经幡五色标记 */
.flag-blue { background: var(--f-blue); }
.flag-white { background: var(--f-white); }
.flag-red { background: var(--f-red); }
.flag-green { background: var(--f-green); }
.flag-yellow { background: var(--f-yellow); }
.flag-flame { background: var(--flame); }

/* ============ 7. 页脚 ============ */
.site-footer {
  margin-top: var(--gap-lg);
  background: var(--night-2);
  border-top: var(--bd) solid var(--gold);
}

.banner-strip {
  display: flex;
  height: 14px;
  border-bottom: var(--bd) solid var(--line);
}
.banner-strip__cell { flex: 1 1 0; height: 100%; }

.footer-inner {
  max-width: var(--shell);
  margin: 0 auto;
  padding: 56px 24px 32px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr 1.2fr;
  gap: 40px;
}

.footer-brand__name {
  margin: 0 0 10px;
  font-family: var(--font-title);
  font-weight: 900;
  font-size: 24px;
  letter-spacing: .02em;
  color: var(--gold);
}
.footer-brand__line {
  margin: 0 0 12px;
  max-width: 34ch;
  font-size: 14px;
  color: var(--gray);
}
.footer-brand__meta {
  margin: 0;
  font-size: 12px;
  letter-spacing: .16em;
  color: var(--f-yellow);
}

.footer-col__title {
  margin: 0 0 14px;
  font-size: 12px;
  font-weight: 900;
  letter-spacing: .24em;
  color: var(--gray);
}
.footer-col__title::before {
  content: "";
  display: inline-block;
  width: 10px;
  height: 10px;
  margin-right: 8px;
  background: var(--flame);
  vertical-align: middle;
}

.footer-links li { margin-bottom: 8px; }
.footer-links a {
  font-size: 14px;
  color: var(--f-white);
  border-bottom: 2px solid transparent;
  padding-bottom: 2px;
  transition: color .12s ease, border-color .12s ease;
}
.footer-links a:hover,
.footer-links a:focus-visible { color: var(--gold); border-bottom-color: var(--gold); }

.footer-contact {
  margin: 0 0 8px;
  font-size: 14px;
  color: var(--f-white);
  word-break: break-word;
}
.footer-note {
  margin: 16px 0 0;
  max-width: 40ch;
  font-size: 12px;
  line-height: 1.8;
  color: var(--gray);
}

.footer-base {
  margin-top: var(--gap-sm);
  padding-top: 20px;
  border-top: 2px solid var(--line);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px 24px;
}
.footer-legal {
  margin: 0;
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--gray);
}
.footer-legal-links { display: flex; flex-wrap: wrap; gap: 16px; }
.footer-legal-links a { font-size: 12px; color: var(--gray); }
.footer-legal-links a:hover,
.footer-legal-links a:focus-visible { color: var(--gold); }

/* ============ 8. 通用组件 ============ */
.stack-panel {
  border: var(--bd) solid var(--line);
  background: var(--night-2);
  box-shadow: var(--hard);
  padding: 32px;
}
.stack-panel + .stack-panel { margin-top: var(--gap-sm); }

.panel-shift { margin-left: 24px; }

.chapter {
  display: flex;
  align-items: flex-start;
  gap: 20px;
}
.chapter__no {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 48px;
  line-height: 1;
  letter-spacing: -.02em;
  color: var(--gold);
}
.chapter__body { flex: 1 1 auto; min-width: 0; }

.ribbon {
  display: flex;
  border: var(--bd) solid var(--line);
  background: #0A1029;
  box-shadow: var(--hard);
  overflow-x: auto;
}
.ribbon__cell {
  flex: 1 0 200px;
  padding: 20px;
  border-right: 2px solid var(--line);
}
.ribbon__cell:last-child { border-right: 0; }

.compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  border: var(--bd) solid var(--line);
  box-shadow: var(--hard);
}
.compare__side { padding: 24px; background: var(--night-2); }
.compare__side + .compare__side { border-left: var(--bd) solid var(--line); }

.stat-band {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  border: var(--bd) solid var(--line);
  background: var(--night-2);
  box-shadow: var(--hard);
}
.stat { padding: 24px; border-right: 2px solid var(--line); }
.stat:last-child { border-right: 0; }
.stat__num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 48px;
  line-height: 1;
  color: var(--gold);
}
.stat__label { margin-top: 8px; font-size: 14px; color: var(--gray); }

.tag-strip { display: flex; flex-wrap: wrap; gap: 8px; }
.tag {
  padding: 6px 12px;
  border: 2px solid var(--line);
  background: transparent;
  color: var(--gray);
  font-size: 12px;
  letter-spacing: .2em;
  cursor: pointer;
  transition: border-color .12s ease, color .12s ease, background-color .12s ease;
}
.tag:hover { border-color: var(--gold); color: var(--gold-soft); }
.tag[aria-pressed="true"] {
  border-color: var(--gold);
  color: var(--gold);
  background: #131C46;
}

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding: 20px 0;
  font-size: 12px;
  letter-spacing: .12em;
  color: var(--gray);
}
.breadcrumb a { color: var(--f-white); }
.breadcrumb a:hover { color: var(--gold); }

.figure {
  display: block;
  margin: 0;
  border: var(--bd) solid var(--line);
  background: #0A1029;
  box-shadow: var(--hard);
}
.figure__media {
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background: linear-gradient(135deg, #101838, #182253);
}
.figure__media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.figure__caption {
  padding: 12px 16px;
  border-top: 2px solid var(--line);
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--gray);
}

.toc { position: sticky; top: calc(var(--nav-top-h) + var(--nav-main-h) + 24px); }
.toc__link {
  display: block;
  padding: 6px 0 6px 12px;
  border-left: 3px solid var(--line);
  font-size: 14px;
  color: var(--gray);
  transition: border-color .12s ease, color .12s ease;
}
.toc__link:hover { color: var(--f-white); border-left-color: var(--gold-soft); }
.toc__link[aria-current="true"] { border-left-color: var(--gold); color: var(--gold); }

.is-hidden { display: none !important; }

/* ============ 9. 阅读进度条 ============ */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  z-index: 120;
  background: rgba(42, 53, 112, .55);
  pointer-events: none;
}
.scroll-progress__fill {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--f-blue), var(--f-white), var(--f-red), var(--f-green), var(--f-yellow), var(--gold));
  transition: width .1s linear;
}

/* ============ 10. 响应式 ============ */
@media (max-width: 1024px) {
  .brand-tagline { display: none; }
  .footer-grid { grid-template-columns: 1.2fr 1fr 1fr; gap: 32px; }
  .footer-col--contact { grid-column: span 3; }
  .footer-note { max-width: 60ch; }
}

@media (max-width: 900px) {
  .grid-12 { gap: 20px; }
  .col-7, .col-5 { grid-column: span 12; }
  .compare { grid-template-columns: 1fr; }
  .compare__side + .compare__side { border-left: 0; border-top: var(--bd) solid var(--line); }
}

@media (max-width: 880px) {
  .nav-toggle { display: inline-flex; }
  .nav-list {
    position: fixed;
    top: calc(var(--nav-top-h) + var(--nav-main-h));
    left: 0;
    right: 0;
    display: block;
    padding: 16px 20px 24px;
    max-height: calc(100vh - var(--nav-top-h) - var(--nav-main-h));
    overflow-y: auto;
    background: var(--night-2);
    border-bottom: var(--bd) solid var(--gold);
    box-shadow: 0 8px 0 rgba(4, 8, 22, .5);
    transform: translateY(-10px);
    opacity: 0;
    visibility: hidden;
    transition: opacity .16s ease, transform .16s ease, visibility .16s ease;
  }
  .nav-list[data-open="true"] {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
  }
  .nav-link {
    display: flex;
    width: 100%;
    margin-bottom: 8px;
    padding: 12px 14px;
    border-color: var(--line);
    font-size: 15px;
  }
  .nav-link[aria-current="page"] { border-color: var(--gold); }
  .nav-main__inner { justify-content: space-between; }
  .nav-cta { margin-left: auto; }
  .quick-jumps {
    flex: 1 1 auto;
    overflow-x: auto;
    padding-bottom: 2px;
  }
}

@media (max-width: 640px) {
  :root {
    --nav-top-h: 40px;
    --nav-main-h: 56px;
    --gap-lg: 64px;
    --gap-md: 40px;
    --gap-sm: 28px;
  }
  body { font-size: 16px; }
  .nav-top__inner, .nav-main__inner, .shell, .footer-inner { padding-left: 16px; padding-right: 16px; }
  .utility-zone { display: none; }
  .stack-panel { padding: 22px; }
  .panel-shift { margin-left: 0; }
  .chapter { gap: 14px; }
  .chapter__no { font-size: 32px; }
  .stat__num { font-size: 32px; }
  .footer-grid { grid-template-columns: 1fr; gap: 28px; }
  .footer-col--contact { grid-column: auto; }
  .footer-base { margin-top: 28px; }
}

/* ============ 11. 减少动效 ============ */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
    scroll-behavior: auto !important;
  }
  .scroll-progress__fill { transition: none; }
  .btn:hover { transform: none; }
}