/* ==========================================================================
   启博EPN · 共享样式 /assets/site.css
   奶油纸白 × 深靛蓝 × 高原藏红 × 暖沙金 × 青绿
   ========================================================================== */

/* 1. 设计令牌 ------------------------------------------------------------- */
:root {
  --paper: #F7F1E4;
  --indigo: #16233F;
  --indigo-deep: #0F1A30;
  --red: #B33A2B;
  --red-deep: #8E2C20;
  --gold: #D9A441;
  --gold-soft: #E8B95C;
  --gold-ink: #8A6115;
  --teal: #2E7D6E;
  --line: #D9D4C8;
  --ink: #2A211C;
  --mist: #8FA3BF;
  --glass: #FFFFFF;

  --paper-72: rgba(247, 241, 228, 0.72);
  --paper-60: rgba(247, 241, 228, 0.60);
  --paper-14: rgba(247, 241, 228, 0.14);
  --paper-34: rgba(247, 241, 228, 0.34);

  --font-head: "Noto Sans SC", "Source Han Sans SC", "Microsoft YaHei", sans-serif;
  --font-body: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: "IBM Plex Mono", "JetBrains Mono", "SFMono-Regular", ui-monospace, monospace;

  --shell: 1360px;
  --gutter: clamp(18px, 4.4vw, 56px);
  --rail-h: 78px;
  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
  --dur: 0.2s;
}

/* 2. Reset ---------------------------------------------------------------- */
*,
*::before,
*::after { box-sizing: border-box; }

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

body {
  margin: 0;
  background-color: var(--paper);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.85;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4, h5, h6, p, figure, blockquote, dl, dd { margin: 0; }

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

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

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

button {
  background: none;
  border: 0;
  padding: 0;
  cursor: pointer;
}

a { color: inherit; text-decoration: none; }

hr { border: 0; }

/* 3. 中文排版 ------------------------------------------------------------- */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-head);
  font-weight: 800;
  color: var(--indigo);
  line-height: 1.12;
  letter-spacing: -0.02em;
}

h2 { font-size: clamp(24px, 3vw, 36px); }
h3 { font-size: clamp(19px, 2vw, 24px); font-weight: 700; line-height: 1.3; }
h4 { font-size: clamp(16px, 1.5vw, 18px); font-weight: 700; line-height: 1.4; }

p { line-height: 1.85; }

::selection {
  background-color: rgba(179, 58, 43, 0.18);
  color: var(--indigo);
}

/* 4. 焦点可见性 ----------------------------------------------------------- */
:focus-visible {
  outline: 2px solid var(--red);
  outline-offset: 3px;
  border-radius: 2px;
}

.site-header :focus-visible,
.site-footer :focus-visible { outline-color: var(--gold); }

#main-content { scroll-margin-top: calc(var(--rail-h) + 16px); }

/* 5. 布局工具 ------------------------------------------------------------- */
.shell {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.section { padding-block: clamp(48px, 7vw, 96px); }

.section-head {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  justify-content: space-between;
  gap: 18px;
  margin-bottom: clamp(24px, 3.4vw, 44px);
}

.grid {
  display: grid;
  gap: clamp(16px, 2.4vw, 28px);
}

.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)); }

.rule {
  height: 1px;
  background-color: var(--line);
  border: 0;
  margin: 0;
}

.u-lede {
  max-width: 34em;
  font-size: clamp(16px, 1.6vw, 19px);
  line-height: 1.8;
  color: #4A4238;
}

.u-mono {
  font-family: var(--font-mono);
  letter-spacing: 0.08em;
}

/* 6. 页眉 ---------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 80;
  background-color: var(--indigo);
  color: var(--paper);
  border-bottom: 1px solid var(--paper-14);
  transition: box-shadow var(--dur) var(--ease);
}

.site-header.is-scrolled {
  box-shadow: 0 12px 34px -18px rgba(10, 16, 30, 0.85);
}

.scroll-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 2px;
  background-image: linear-gradient(90deg, var(--red), var(--gold));
  transform: scaleX(0);
  transform-origin: 0 50%;
  pointer-events: none;
  z-index: 3;
}

.skip-link {
  position: absolute;
  left: var(--gutter);
  top: -72px;
  z-index: 200;
  padding: 10px 18px;
  background-color: var(--gold);
  color: var(--indigo);
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.08em;
  border-radius: 0 0 3px 3px;
  transition: top var(--dur) var(--ease);
}

.skip-link:focus { top: 0; }

.header-rail {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: clamp(14px, 3vw, 40px);
  width: 100%;
  max-width: var(--shell);
  min-height: var(--rail-h);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.brand-block { display: flex; align-items: center; min-width: 0; }

.brand-link {
  display: inline-flex;
  align-items: center;
  gap: 13px;
  padding-block: 8px;
}

.brand-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex: 0 0 40px;
  width: 40px;
  height: 40px;
  background-color: var(--red);
  color: var(--paper);
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.06em;
  border-radius: 2px 13px 2px 13px;
  transition: background-color var(--dur) var(--ease), border-radius var(--dur) var(--ease);
}

.brand-link:hover .brand-mark,
.brand-link:focus-visible .brand-mark {
  background-color: var(--gold);
  color: var(--indigo);
  border-radius: 13px 2px 13px 2px;
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.25;
  min-width: 0;
}

.brand-name {
  font-family: var(--font-head);
  font-size: 20px;
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--paper);
}

.brand-note {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.12em;
  color: var(--paper-60);
  white-space: nowrap;
}

.nav-shell {
  display: flex;
  align-items: center;
  gap: clamp(12px, 2.4vw, 32px);
  margin-left: auto;
}

.main-nav { display: block; }

.nav-list {
  display: flex;
  align-items: center;
  gap: clamp(2px, 1vw, 16px);
}

.nav-item { display: block; }

.nav-link {
  position: relative;
  display: inline-block;
  padding: 8px 2px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.08em;
  line-height: 1.4;
  color: var(--paper-72);
  transition: color var(--dur) var(--ease);
}

.nav-link::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 2px;
  height: 1px;
  background-color: var(--gold);
  transform: scaleX(0);
  transform-origin: 0 50%;
  transition: transform var(--dur) var(--ease), background-color var(--dur) var(--ease);
}

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

.nav-link:hover::after,
.nav-link:focus-visible::after { transform: scaleX(1); }

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

.nav-link[aria-current="page"]::after {
  height: 2px;
  background-color: var(--red);
  transform: scaleX(1);
}

.header-tools {
  display: flex;
  align-items: center;
  gap: 10px;
  padding-left: clamp(8px, 1.6vw, 20px);
  border-left: 1px solid var(--paper-14);
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  border: 1px solid var(--paper-34);
  border-radius: 2px;
  color: var(--paper);
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.12em;
  transition: border-color var(--dur) var(--ease), color var(--dur) var(--ease);
}

.nav-toggle:hover,
.nav-toggle:focus-visible {
  border-color: var(--gold);
  color: var(--gold);
}

.nav-toggle-label { line-height: 1; }

.nav-toggle-icon {
  position: relative;
  display: inline-block;
  width: 16px;
  height: 10px;
}

.nav-toggle-icon span {
  position: absolute;
  left: 0;
  right: 0;
  height: 1.5px;
  background-color: currentColor;
  transition: transform var(--dur) var(--ease), opacity var(--dur) var(--ease);
}

.nav-toggle-icon span:nth-child(1) { top: 0; }
.nav-toggle-icon span:nth-child(2) { top: 4.25px; }
.nav-toggle-icon span:nth-child(3) { top: 8.5px; }

.site-header[data-open="true"] .nav-toggle-icon span:nth-child(1) {
  transform: translateY(4.25px) rotate(45deg);
}

.site-header[data-open="true"] .nav-toggle-icon span:nth-child(2) { opacity: 0; }

.site-header[data-open="true"] .nav-toggle-icon span:nth-child(3) {
  transform: translateY(-4.25px) rotate(-45deg);
}

.site-header[data-open="true"] .nav-toggle {
  border-color: var(--gold);
  color: var(--gold);
}

/* 7. 按钮 ---------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 20px;
  border: 1px solid transparent;
  border-radius: 2px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  line-height: 1.2;
  letter-spacing: 0.08em;
  text-align: center;
  text-decoration: none;
  cursor: pointer;
  transition: background-color var(--dur) var(--ease),
              color var(--dur) var(--ease),
              border-color var(--dur) var(--ease);
}

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

.btn--gold:hover,
.btn--gold:focus-visible {
  background-color: var(--gold-soft);
  border-color: var(--gold-soft);
}

.btn--outline {
  background-color: transparent;
  border-color: var(--paper-34);
  color: var(--paper);
}

.btn--outline:hover,
.btn--outline:focus-visible {
  border-color: var(--gold);
  color: var(--gold);
}

.btn--solid {
  background-color: var(--red);
  border-color: var(--red);
  color: var(--paper);
}

.btn--solid:hover,
.btn--solid:focus-visible {
  background-color: var(--red-deep);
  border-color: var(--red-deep);
}

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

.btn--ink:hover,
.btn--ink:focus-visible {
  background-color: var(--indigo-deep);
  border-color: var(--indigo-deep);
}

.btn--quiet {
  background-color: transparent;
  border-color: var(--line);
  color: var(--indigo);
}

.btn--quiet:hover,
.btn--quiet:focus-visible {
  border-color: var(--red);
  color: var(--red);
}

/* 8. 通用组件 ------------------------------------------------------------ */
.chapter {
  display: inline-flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 14px;
}

.chapter-no {
  display: inline-block;
  padding: 3px 9px;
  background-color: var(--red);
  color: var(--paper);
  font-family: var(--font-mono);
  font-size: 12.5px;
  font-weight: 500;
  letter-spacing: 0.08em;
  line-height: 1.5;
  border-radius: 2px;
}

.eyebrow {
  display: block;
  margin-bottom: 10px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.18em;
  color: var(--teal);
}

.card {
  position: relative;
  padding: clamp(18px, 2.4vw, 30px);
  background-color: var(--glass);
  border: 1px solid var(--line);
  border-radius: 3px;
  transition: border-color var(--dur) var(--ease),
              box-shadow var(--dur) var(--ease);
}

.card:hover,
.card:focus-within {
  border-color: var(--red);
  box-shadow: 0 16px 38px -26px rgba(22, 35, 63, 0.7);
}

.card--glass {
  background-color: rgba(255, 255, 255, 0.62);
  border-color: rgba(255, 255, 255, 0.72);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background-color: rgba(217, 164, 65, 0.14);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  line-height: 1.7;
  color: var(--gold-ink);
}

.tag--gold {
  border-color: rgba(217, 164, 65, 0.45);
  background-color: rgba(217, 164, 65, 0.18);
  color: var(--gold-ink);
}

.tag--teal {
  border-color: rgba(46, 125, 110, 0.32);
  background-color: rgba(46, 125, 110, 0.1);
  color: var(--teal);
}

.breadcrumbs { padding-top: clamp(18px, 3vw, 30px); }

.breadcrumb-list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.08em;
  color: #6D6558;
}

.breadcrumb-list li { display: flex; align-items: center; }

.breadcrumb-list li + li::before {
  content: "/";
  margin: 0 8px;
  color: #B8B1A2;
}

.breadcrumb-list a { transition: color var(--dur) var(--ease); }

.breadcrumb-list a:hover,
.breadcrumb-list a:focus-visible { color: var(--red); }

.prose {
  max-width: 38em;
  font-size: 16px;
  line-height: 1.9;
  color: var(--ink);
}

.prose > * + * { margin-top: 1.1em; }

.prose h2,
.prose h3 { margin-top: 1.8em; }

.prose ul { list-style: disc; padding-left: 1.4em; }
.prose ol { list-style: decimal; padding-left: 1.5em; }
.prose li + li { margin-top: 0.5em; }

.prose a {
  color: var(--red);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
}

.prose a:hover { color: var(--red-deep); }

.media-frame {
  position: relative;
  display: block;
  overflow: hidden;
  width: 100%;
  aspect-ratio: 16 / 10;
  border-radius: 3px;
  background-image: linear-gradient(150deg, rgba(22, 35, 63, 0.16), rgba(217, 164, 65, 0.22));
}

.media-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.media-frame--wide { aspect-ratio: 21 / 9; }
.media-frame--tall { aspect-ratio: 3 / 4; }
.media-frame--square { aspect-ratio: 1 / 1; }

.media-frame--glass::after {
  content: "";
  position: absolute;
  inset: 0;
  background-image: linear-gradient(180deg, rgba(22, 35, 63, 0) 42%, rgba(22, 35, 63, 0.58));
  pointer-events: none;
}

.media-frame__caption {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 1;
  padding: 14px 16px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--paper);
}

/* 9. 页脚 ---------------------------------------------------------------- */
.site-footer {
  margin-top: clamp(56px, 9vw, 120px);
  background-color: var(--indigo);
  color: var(--paper);
}

.footer-inner {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding: clamp(40px, 6vw, 80px) var(--gutter) clamp(24px, 3vw, 36px);
}

.footer-brandbar {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 14px;
  margin-bottom: clamp(26px, 4vw, 46px);
}

.footer-brand {
  font-family: var(--font-head);
  font-size: clamp(26px, 3.4vw, 40px);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.05;
  color: var(--paper);
}

.footer-tag {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.16em;
  color: var(--gold);
}

.footer-top {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: clamp(20px, 3vw, 44px);
  padding-bottom: clamp(26px, 4vw, 46px);
  border-bottom: 1px solid var(--paper-14);
}

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

.footer-col-title {
  margin-bottom: 14px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  font-weight: 500;
  letter-spacing: 0.16em;
  line-height: 1.6;
  color: var(--gold);
}

.footer-links li + li { margin-top: 9px; }

.footer-link {
  display: inline-block;
  font-size: 14px;
  line-height: 1.7;
  color: var(--paper-72);
  transition: color var(--dur) var(--ease);
}

.footer-link:hover,
.footer-link:focus-visible { color: var(--paper); }

.footer-contact {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: clamp(16px, 3vw, 40px);
  padding: clamp(24px, 3.5vw, 40px) 0 0;
}

.footer-contact-item { min-width: 0; }

.footer-k {
  display: block;
  margin-bottom: 6px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.16em;
  color: var(--mist);
}

.footer-v {
  display: block;
  font-size: 14px;
  line-height: 1.7;
  color: var(--paper);
  word-break: break-word;
}

.footer-note {
  margin-top: 18px;
  max-width: 52em;
  font-size: 12.5px;
  line-height: 1.8;
  color: var(--paper-60);
}

.footer-base {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px 24px;
  margin-top: clamp(18px, 2.5vw, 28px);
  padding-top: clamp(16px, 2vw, 24px);
  border-top: 1px solid var(--paper-14);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: rgba(247, 241, 228, 0.5);
}

.footer-legal,
.footer-copy { line-height: 1.7; }

/* 10. 响应式 ------------------------------------------------------------- */
@media (max-width: 1040px) {
  :root { --rail-h: 66px; }

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

  .nav-shell {
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    margin-left: 0;
    padding: 18px var(--gutter) 26px;
    background-color: var(--indigo);
    border-top: 1px solid var(--paper-14);
    border-bottom: 3px solid var(--gold);
    box-shadow: 0 30px 50px -32px rgba(10, 16, 30, 0.9);
    max-height: calc(100vh - var(--rail-h));
    overflow-y: auto;
  }

  .site-header[data-open="true"] .nav-shell { display: flex; }

  .main-nav { width: 100%; }

  .nav-list {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    width: 100%;
    gap: 0;
    margin-bottom: 18px;
  }

  .nav-link {
    display: block;
    padding: 13px 4px;
    font-size: 14px;
    letter-spacing: 0.06em;
    color: var(--paper);
    border-bottom: 1px solid var(--paper-14);
  }

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

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

  .header-tools {
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
    width: 100%;
    padding-left: 0;
    padding-top: 18px;
    border-left: 0;
    border-top: 1px solid var(--paper-14);
  }

  .header-tools .btn { width: 100%; }
}

@media (max-width: 900px) {
  .grid--3,
  .grid--4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }

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

@media (max-width: 620px) {
  body { font-size: 15.5px; }

  .grid--2,
  .grid--3,
  .grid--4 { grid-template-columns: 1fr; }

  .nav-list { grid-template-columns: 1fr; }

  .brand-note { display: none; }

  .brand-name { font-size: 18px; }

  .brand-mark {
    flex-basis: 34px;
    width: 34px;
    height: 34px;
    font-size: 11px;
  }

  .breadcrumb-list { font-size: 10.5px; }

  .footer-contact { grid-template-columns: 1fr; }

  .footer-base {
    flex-direction: column;
    align-items: flex-start;
  }
}

@media (max-width: 420px) {
  .nav-toggle-label { display: none; }
}

/* 11. 动效减弱 ----------------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    transition-duration: 0.001ms !important;
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
  }
}