/* ==========================================================================
   开元指南 · 共享样式  /assets/site.css
   纸张叠层 / 印刷边框 / 铜绿与鎏金 / 档案编号
   ========================================================================== */

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

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

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

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

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

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

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

table { border-collapse: collapse; width: 100%; }

/* ---------- tokens ---------- */
:root {
  --paper: #F7F3E8;
  --paper-card: #FFFDF7;
  --copper: #1F6F5C;
  --copper-deep: #145246;
  --copper-soft: #D8E8E1;
  --gold: #C79A2E;
  --gold-bright: #E4B94A;
  --indigo: #284B7A;
  --ink: #1A1A18;
  --fog: #6B6A63;

  --line: rgba(31, 111, 92, 0.24);
  --line-strong: rgba(20, 82, 70, 0.45);
  --line-gold: rgba(199, 154, 46, 0.42);

  --shadow-card: 0 1px 0 rgba(26, 26, 24, 0.05), 0 12px 26px -18px rgba(20, 82, 70, 0.55);
  --shadow-lift: 0 2px 0 rgba(26, 26, 24, 0.06), 0 18px 34px -20px rgba(20, 82, 70, 0.6);

  --font-sans: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  --font-mono: ui-monospace, "SFMono-Regular", "IBM Plex Mono", "Roboto Mono", Menlo, Consolas, monospace;

  --w-max: 1180px;
  --pad-x: clamp(16px, 4vw, 40px);
  --nav-break: 900px;
}

/* ---------- base ---------- */
body {
  background-color: var(--paper);
  background-image:
    repeating-linear-gradient(90deg, rgba(31, 111, 92, 0.035) 0 1px, transparent 1px 64px),
    radial-gradient(120% 60% at 88% -10%, rgba(199, 154, 46, 0.13), transparent 62%);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.75;
  letter-spacing: 0.01em;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 {
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.22;
  color: var(--copper-deep);
  text-wrap: balance;
}

p { text-wrap: pretty; }

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

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

/* ---------- skip link ---------- */
.skip-link {
  position: fixed;
  top: 10px;
  left: -9999px;
  z-index: 200;
  padding: 10px 18px;
  background: var(--copper-deep);
  color: var(--paper-card);
  font-size: 13px;
  letter-spacing: 0.08em;
  border: 1px solid var(--gold-bright);
  transition: left 0.18s ease;
}

.skip-link:focus,
.skip-link:focus-visible {
  left: 12px;
  outline: 2px solid var(--gold-bright);
  outline-offset: 2px;
}

/* ==========================================================================
   头部
   ========================================================================== */
.site-header {
  position: relative;
  z-index: 30;
  background: var(--paper);
}

/* 通道色带 */
.utility {
  background: var(--copper-deep);
  color: var(--paper);
  border-bottom: 1px solid rgba(199, 154, 46, 0.45);
}

.utility-inner {
  max-width: var(--w-max);
  margin: 0 auto;
  padding: 8px var(--pad-x);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

.channel-badge {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.16em;
  color: rgba(247, 243, 232, 0.92);
  text-transform: uppercase;
}

.badge-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--gold-bright);
  box-shadow: 0 0 0 3px rgba(228, 185, 74, 0.2);
  flex: none;
}

.utility-links {
  display: flex;
  align-items: center;
  gap: 18px;
}

.utility-link {
  font-size: 12px;
  letter-spacing: 0.1em;
  color: rgba(247, 243, 232, 0.78);
  border-bottom: 1px solid transparent;
  padding-bottom: 1px;
  transition: color 0.2s ease, border-color 0.2s ease;
}

.utility-link:hover,
.utility-link:focus-visible {
  color: var(--gold-bright);
  border-bottom-color: var(--gold-bright);
}

.utility-link--mono {
  font-family: var(--font-mono);
  letter-spacing: 0.2em;
  color: var(--gold-bright);
}

/* 刊头 */
.masthead {
  position: relative;
  background: var(--paper);
  border-bottom: 1px solid var(--line);
}

.masthead-inner {
  max-width: var(--w-max);
  margin: 0 auto;
  padding: 20px var(--pad-x) 18px;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 16px;
}

.masthead-side {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.22em;
  color: var(--fog);
  text-transform: uppercase;
}

.masthead-side--end { text-align: right; }

.brand {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
  text-align: center;
  justify-self: center;
}

.brand-name {
  font-size: clamp(26px, 3.3vw, 42px);
  font-weight: 800;
  line-height: 1.06;
  letter-spacing: 0.1em;
  color: var(--copper-deep);
}

.brand-sub {
  font-family: var(--font-mono);
  font-size: 9.5px;
  letter-spacing: 0.34em;
  color: var(--gold);
  text-transform: uppercase;
}

.brand::after {
  content: "";
  width: 38px;
  height: 2px;
  margin-top: 7px;
  background: var(--gold);
}

.brand:hover .brand-name { color: var(--copper); }

/* 移动导航按钮 */
.nav-toggle {
  display: none;
  position: absolute;
  right: var(--pad-x);
  top: 50%;
  transform: translateY(-50%);
  align-items: center;
  gap: 9px;
  padding: 9px 13px;
  background: var(--paper-card);
  border: 1px solid var(--copper);
  color: var(--copper-deep);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  z-index: 5;
}

.nav-toggle:focus-visible {
  outline: 2px solid var(--indigo);
  outline-offset: 2px;
}

.nav-toggle-bars {
  position: relative;
  display: inline-block;
  width: 16px;
  height: 2px;
  background: currentColor;
  transition: background 0.2s ease;
}

.nav-toggle-bars::before,
.nav-toggle-bars::after {
  content: "";
  position: absolute;
  left: 0;
  width: 16px;
  height: 2px;
  background: currentColor;
  transition: transform 0.24s ease, opacity 0.24s ease;
}

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

.nav-toggle[aria-expanded="true"] .nav-toggle-bars { background: transparent; }
.nav-toggle[aria-expanded="true"] .nav-toggle-bars::before { transform: translateY(5px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle-bars::after { transform: translateY(-5px) rotate(-45deg); }

/* 栏目条 */
.header-nav {
  display: block;
  background: var(--paper-card);
  border-bottom: 3px double var(--copper-deep);
}

.nav-inner {
  max-width: var(--w-max);
  margin: 0 auto;
  padding: 0 var(--pad-x);
}

.nav-list {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: stretch;
}

.nav-item { position: relative; }

.nav-item + .nav-item::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 1px;
  height: 14px;
  transform: translateY(-50%);
  background: var(--line);
}

.nav-link {
  display: inline-flex;
  align-items: baseline;
  gap: 7px;
  padding: 13px 18px;
  font-size: 14px;
  font-weight: 500;
  letter-spacing: 0.04em;
  color: var(--ink);
  border-bottom: 3px solid transparent;
  transition: color 0.2s ease, background 0.2s ease, border-color 0.2s ease;
}

.nav-index {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.12em;
  color: var(--gold);
}

.nav-link:hover {
  color: var(--copper);
  border-bottom-color: var(--copper-soft);
  background: rgba(216, 232, 225, 0.4);
}

.nav-link[aria-current="page"] {
  color: var(--copper-deep);
  border-bottom-color: var(--gold);
  background: linear-gradient(180deg, rgba(216, 232, 225, 0), rgba(216, 232, 225, 0.7));
}

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

.nav-link:focus-visible {
  outline: 2px solid var(--indigo);
  outline-offset: -2px;
}

/* 悬浮帮助入口（频道栏第三位 · 固定） */
.help-float {
  position: fixed;
  right: 18px;
  bottom: 18px;
  z-index: 45;
  display: inline-flex;
  align-items: center;
  gap: 9px;
  padding: 11px 15px;
  background: var(--copper-deep);
  color: var(--paper-card);
  border: 1px solid var(--gold);
  box-shadow: 0 12px 26px -14px rgba(20, 82, 70, 0.85);
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0.1em;
  animation: help-breathe 4.6s ease-in-out infinite;
  transition: transform 0.2s ease, background 0.2s ease;
}

.help-float__index {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.14em;
  color: var(--gold-bright);
  padding-right: 9px;
  border-right: 1px solid var(--line-gold);
}

.help-float__text { white-space: nowrap; }

.help-float:hover,
.help-float:focus-visible {
  background: var(--copper);
  transform: translateY(-2px);
}

.help-float:focus-visible {
  outline: 2px solid var(--gold-bright);
  outline-offset: 2px;
}

@keyframes help-breathe {
  0%, 100% { box-shadow: 0 12px 26px -14px rgba(20, 82, 70, 0.85), 0 0 0 0 rgba(199, 154, 46, 0.4); }
  50% { box-shadow: 0 12px 26px -14px rgba(20, 82, 70, 0.85), 0 0 0 7px rgba(199, 154, 46, 0); }
}

/* ==========================================================================
   页脚
   ========================================================================== */
.site-footer {
  margin-top: clamp(48px, 7vw, 96px);
  background: var(--copper-deep);
  color: var(--paper);
  border-top: 6px double var(--gold);
}

.footer-inner {
  max-width: var(--w-max);
  margin: 0 auto;
  padding: clamp(32px, 5vw, 58px) var(--pad-x) 30px;
  display: grid;
  grid-template-columns: minmax(230px, 1fr) minmax(0, 2.3fr);
  gap: clamp(26px, 4vw, 60px);
}

.footer-brand-name {
  font-size: clamp(24px, 2.6vw, 30px);
  font-weight: 800;
  letter-spacing: 0.12em;
  color: var(--paper-card);
  line-height: 1.1;
}

.footer-tag {
  margin-top: 10px;
  font-size: 13.5px;
  line-height: 1.75;
  max-width: 26em;
  color: rgba(247, 243, 232, 0.72);
}

.footer-mono {
  margin-top: 16px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.24em;
  color: var(--gold-bright);
}

.footer-cols {
  display: grid;
  grid-template-columns: 1.5fr 0.85fr 0.85fr;
  gap: clamp(20px, 3vw, 40px);
}

.footer-col-title {
  margin-bottom: 12px;
  padding-bottom: 9px;
  border-bottom: 1px solid var(--line-gold);
  font-family: var(--font-mono);
  font-size: 10.5px;
  font-weight: 600;
  letter-spacing: 0.26em;
  color: var(--gold-bright);
  text-transform: uppercase;
}

.footer-list { display: grid; gap: 9px; }

.footer-contact-line {
  font-size: 13px;
  line-height: 1.7;
  color: rgba(247, 243, 232, 0.78);
  word-break: break-word;
}

.footer-link {
  font-size: 13.5px;
  color: rgba(247, 243, 232, 0.84);
  border-bottom: 1px solid transparent;
  padding-bottom: 1px;
  transition: color 0.2s ease, border-color 0.2s ease;
}

.footer-link:hover,
.footer-link:focus-visible {
  color: var(--gold-bright);
  border-bottom-color: var(--gold-bright);
}

.footer-link:focus-visible {
  outline: 2px solid var(--gold-bright);
  outline-offset: 2px;
}

.footer-bottom {
  max-width: var(--w-max);
  margin: 0 auto;
  padding: 16px var(--pad-x) 28px;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px 20px;
  border-top: 1px solid rgba(247, 243, 232, 0.18);
  font-size: 12px;
  letter-spacing: 0.07em;
  color: rgba(247, 243, 232, 0.62);
}

.footer-copy { max-width: 42em; }

.footer-icp {
  font-family: var(--font-mono);
  letter-spacing: 0.12em;
  color: rgba(247, 243, 232, 0.78);
}

/* ==========================================================================
   共享排版与组件
   ========================================================================== */
.container {
  width: 100%;
  max-width: var(--w-max);
  margin: 0 auto;
  padding: 0 var(--pad-x);
}

.section { padding: clamp(36px, 5.5vw, 72px) 0; }

.kicker {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--copper);
}

.kicker::before {
  content: "";
  width: 22px;
  height: 2px;
  background: var(--gold);
  flex: none;
}

.prose {
  max-width: 68ch;
  font-size: 17px;
  line-height: 1.78;
  color: var(--ink);
}

.prose > * + * { margin-top: 1em; }

.prose h2 {
  font-size: clamp(21px, 2.4vw, 27px);
  margin-top: 1.7em;
  padding-left: 14px;
  border-left: 4px solid var(--copper);
}

.prose h3 {
  font-size: 18px;
  color: var(--copper);
  margin-top: 1.4em;
}

.prose a {
  color: var(--indigo);
  border-bottom: 1px solid rgba(40, 75, 122, 0.42);
}

.prose a:hover { border-bottom-color: var(--indigo); }

.prose strong { color: var(--copper-deep); }

.stack { display: grid; gap: 1rem; }

/* 按钮 */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 22px;
  border: 1.5px solid var(--copper-deep);
  background: var(--paper-card);
  color: var(--copper-deep);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.06em;
  line-height: 1.2;
  transition: background 0.2s ease, color 0.2s ease, border-color 0.2s ease, transform 0.2s ease;
}

.btn:hover {
  background: var(--copper-soft);
  transform: translateY(-1px);
}

.btn:focus-visible {
  outline: 2px solid var(--indigo);
  outline-offset: 2px;
}

.btn--solid {
  background: var(--copper-deep);
  border-color: var(--copper-deep);
  color: var(--paper-card);
}

.btn--solid:hover {
  background: var(--copper);
  border-color: var(--copper);
  color: #FFFFFF;
}

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

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

.btn--ghost {
  background: transparent;
  border-color: var(--gold);
  color: var(--copper-deep);
}

.btn--ghost:hover {
  background: rgba(228, 185, 74, 0.18);
  border-color: var(--gold);
}

.btn--sm {
  padding: 8px 14px;
  font-size: 12.5px;
}

/* 标签 */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  background: var(--copper-soft);
  border: 1px solid rgba(31, 111, 92, 0.26);
  color: var(--copper-deep);
  font-size: 11.5px;
  font-weight: 500;
  letter-spacing: 0.1em;
  line-height: 1.6;
}

.tag--gold {
  background: rgba(228, 185, 74, 0.22);
  border-color: rgba(199, 154, 46, 0.58);
  color: #6B4D06;
}

.tag--indigo {
  background: rgba(40, 75, 122, 0.1);
  border-color: rgba(40, 75, 122, 0.36);
  color: var(--indigo);
}

.tag--mono {
  font-family: var(--font-mono);
  letter-spacing: 0.14em;
}

/* 卡片 */
.card {
  position: relative;
  padding: clamp(18px, 2.4vw, 28px);
  background: var(--paper-card);
  border: 1px solid var(--line);
  box-shadow: var(--shadow-card);
}

.card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 46px;
  height: 3px;
  background: var(--gold);
}

.card-title {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: 0.01em;
  color: var(--copper-deep);
}

/* 面包屑 */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 7px;
  font-size: 12px;
  letter-spacing: 0.07em;
  color: var(--fog);
}

.breadcrumb-link {
  color: var(--indigo);
  border-bottom: 1px solid transparent;
}

.breadcrumb-link:hover { border-bottom-color: var(--indigo); }

.breadcrumb-sep { color: var(--line-strong); }

.breadcrumb-current { color: var(--ink); }

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

.grid--split {
  grid-template-columns: minmax(210px, 288px) minmax(0, 1fr);
  gap: clamp(24px, 4vw, 56px);
  align-items: start;
}

.grid--cards {
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
}

/* 图像容器基础规则 */
.img-frame {
  position: relative;
  overflow: hidden;
  aspect-ratio: 16 / 10;
  background: var(--copper-soft);
  border: 1px solid var(--line);
}

.img-frame > img,
.img-frame > svg {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.img-frame::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(118deg, rgba(31, 111, 92, 0.2), transparent 56%);
  pointer-events: none;
}

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

.img-caption {
  margin-top: 8px;
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--fog);
}

/* 脚本注入：进度条与返回顶部 */
.scroll-meter {
  position: fixed;
  inset: 0 0 auto 0;
  height: 3px;
  z-index: 90;
  background: linear-gradient(90deg, var(--copper), var(--gold-bright));
  transform: scaleX(0);
  transform-origin: 0 50%;
  pointer-events: none;
}

.to-top {
  position: fixed;
  right: 18px;
  bottom: 76px;
  z-index: 44;
  width: 46px;
  height: 46px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: var(--paper-card);
  border: 1px solid var(--gold);
  color: var(--copper-deep);
  font-family: var(--font-mono);
  font-size: 14px;
  letter-spacing: 0.06em;
  box-shadow: var(--shadow-card);
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: opacity 0.22s ease, transform 0.22s ease, visibility 0.22s ease, background 0.2s ease;
}

.to-top[data-visible] {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.to-top:hover { background: var(--copper-soft); }

.to-top:focus-visible {
  outline: 2px solid var(--indigo);
  outline-offset: 2px;
}

/* ==========================================================================
   响应式
   ========================================================================== */
@media (max-width: 1024px) {
  .footer-inner { grid-template-columns: 1fr; }
  .footer-cols { grid-template-columns: 1.5fr 1fr 1fr; }
}

@media (max-width: 900px) {
  body { font-size: 16.5px; }

  .masthead-inner {
    grid-template-columns: 1fr;
    justify-items: center;
    padding: 18px 86px;
  }

  .masthead-side { display: none; }

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

  .header-nav {
    display: none;
    border-bottom: 3px double var(--copper-deep);
    background: var(--copper-soft);
  }

  .header-nav[data-open] { display: block; }

  .nav-inner { padding: 4px var(--pad-x) 14px; }

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

  .nav-item { border-bottom: 1px solid var(--line); }

  .nav-item:last-child { border-bottom: 0; }

  .nav-item + .nav-item::before { display: none; }

  .nav-link {
    display: flex;
    width: 100%;
    padding: 14px 6px;
    font-size: 16px;
    border-bottom: 0;
    border-left: 3px solid transparent;
  }

  .nav-link:hover { border-left-color: var(--copper); }

  .nav-link[aria-current="page"] {
    border-bottom-color: transparent;
    border-left-color: var(--gold);
    background: rgba(255, 253, 247, 0.62);
  }

  .grid--split { grid-template-columns: 1fr; }

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

  .footer-inner { padding-bottom: 22px; }

  .help-float { right: 14px; bottom: 14px; padding: 10px 13px; font-size: 12.5px; }
  .to-top { right: 14px; bottom: 66px; width: 42px; height: 42px; }
}

@media (max-width: 560px) {
  .utility-inner { gap: 6px 10px; }
  .utility-links { gap: 14px; }
  .masthead-inner { padding: 16px 78px; }
  .brand-name { letter-spacing: 0.08em; }
  .footer-cols { grid-template-columns: 1fr; }
  .footer-bottom { flex-direction: column; align-items: flex-start; }
  .prose { font-size: 16px; }
}

/* ---------- 动效偏好 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

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

  .help-float { animation: none; }
  .to-top { transform: none; }
}