/* 四季CN 共享样式 —— /assets/site.css */

/* ---------- 1. Reset & Tokens ---------- */
:root {
  --color-paper: #F4F2EB;
  --color-ink: #101312;
  --color-spring: #0D8F5A;
  --color-summer: #1D6FB8;
  --color-autumn: #D9772E;
  --color-winter: #E8EFED;
  --color-line: #242424;
  --color-muted: #6A6A63;
  --color-fog: #C9C5BC;
  --color-tea: #A97A50;

  --font-serif: "Noto Serif SC", "Source Han Serif SC", "SimSun", "Songti SC", serif;
  --font-sans: "Noto Sans SC", "Source Han Sans SC", "Microsoft YaHei", "PingFang SC", sans-serif;
  --font-mono: "Roboto Mono", "SF Mono", "Cascadia Mono", "Consolas", monospace;

  --header-w: 280px;
  --topbar-h: 64px;
  --search-h: 56px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --dur: 0.24s;
  --container: 1280px;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

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

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.75;
  color: var(--color-line);
  background: var(--color-paper);
}

h1, h2, h3, h4 {
  font-family: var(--font-serif);
  font-weight: 700;
  line-height: 1.35;
  color: var(--color-line);
}

h1 { font-size: clamp(30px, 4.5vw, 52px); letter-spacing: 0.02em; }
h2 { font-size: clamp(24px, 3vw, 34px); letter-spacing: 0.04em; }
h3 { font-size: 20px; letter-spacing: 0.05em; }

p { margin-bottom: 1em; }

a { color: inherit; text-decoration: none; }
ul, ol { list-style: none; }
img, svg { display: block; max-width: 100%; }
button, input { font: inherit; }
button { background: none; border: none; cursor: pointer; }
address { font-style: normal; }

[hidden] { display: none !important; }

::selection { background: var(--color-spring); color: #fff; }

:focus-visible { outline: 2px solid var(--color-spring); outline-offset: 2px; }
.site-header :focus-visible,
.site-footer :focus-visible { outline-color: var(--color-paper); }

/* ---------- 2. 通用工具与排版 ---------- */
.visually-hidden {
  position: absolute !important;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.page-wrap {
  width: min(var(--container), 100%);
  margin-inline: auto;
  padding-inline: clamp(20px, 4vw, 48px);
}

.page-content { max-width: 880px; }
.page-content p { margin-bottom: 1.2em; color: #3a3a3a; }
.page-content a { color: var(--color-summer); border-bottom: 1px solid transparent; transition: border-color var(--dur) var(--ease); }
.page-content a:hover { border-bottom-color: var(--color-summer); }
.page-content ul { margin-bottom: 1.2em; }
.page-content ul li { position: relative; padding-left: 18px; margin-bottom: 6px; }
.page-content ul li::before { content: ""; position: absolute; left: 0; top: 0.8em; width: 8px; height: 1px; background: var(--color-spring); }
.page-content ol { counter-reset: seasonal; margin-bottom: 1.2em; }
.page-content ol li { position: relative; padding-left: 26px; margin-bottom: 6px; counter-increment: seasonal; }
.page-content ol li::before { content: counter(seasonal, decimal-leading-zero); position: absolute; left: 0; top: 0; font-family: var(--font-mono); font-size: 12px; color: var(--color-muted); line-height: 1.9; }

.bg-grid {
  background-image:
    linear-gradient(to right, rgba(36, 36, 36, 0.05) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(36, 36, 36, 0.05) 1px, transparent 1px);
  background-size: 24px 24px;
}

/* ---------- 3. Skip Link ---------- */
.skip-link {
  position: fixed;
  top: -100px;
  left: 8px;
  z-index: 1000;
  padding: 10px 18px;
  background: var(--color-ink);
  color: var(--color-paper);
  font-size: 14px;
  transition: top var(--dur) var(--ease);
}
.skip-link:focus-visible { top: 8px; }

/* ---------- 4. 头部框架导航 ---------- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--topbar-h);
  z-index: 100;
  background: var(--color-ink);
  color: var(--color-paper);
}

.header-bar {
  height: var(--topbar-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 16px 0 20px;
  border-bottom: 1px solid #232726;
}

.brand { display: flex; align-items: center; gap: 12px; min-width: 0; }
.brand-word { display: flex; flex-direction: column; line-height: 1.2; min-width: 0; }
.brand-cn { font-family: var(--font-serif); font-size: 20px; font-weight: 700; letter-spacing: 0.1em; color: var(--color-paper); white-space: nowrap; }
.brand-sub { font-size: 10px; color: #9a9f9c; letter-spacing: 0.12em; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }

.brand-mark {
  position: relative;
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: conic-gradient(var(--color-spring) 0deg 90deg, var(--color-summer) 90deg 180deg, var(--color-autumn) 180deg 270deg, var(--color-winter) 270deg 360deg);
  border: 2px solid var(--color-paper);
  flex-shrink: 0;
}
.brand-mark::before {
  content: "四";
  position: absolute;
  inset: 5px;
  border-radius: 50%;
  background: var(--color-ink);
  color: var(--color-paper);
  display: grid;
  place-items: center;
  font-family: var(--font-serif);
  font-size: 14px;
  line-height: 1;
}

.nav-toggle {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 6px;
  color: var(--color-paper);
}
.nav-toggle-lines { position: relative; display: block; width: 22px; height: 16px; }
.nav-toggle-lines span { position: absolute; left: 0; width: 22px; height: 2px; background: var(--color-paper); transition: transform var(--dur) var(--ease), top var(--dur) var(--ease), opacity var(--dur) var(--ease); }
.nav-toggle-lines span:nth-child(1) { top: 0; }
.nav-toggle-lines span:nth-child(2) { top: 7px; }
.nav-toggle-lines span:nth-child(3) { top: 14px; }
.nav-toggle[aria-expanded="true"] .nav-toggle-lines span:nth-child(1) { top: 7px; transform: rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle-lines span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .nav-toggle-lines span:nth-child(3) { top: 7px; transform: rotate(-45deg); }
.nav-toggle-label { font-size: 10px; letter-spacing: 0.18em; color: var(--color-fog); }

.nav-shell {
  position: fixed;
  top: var(--topbar-h);
  left: 0;
  bottom: 0;
  width: min(320px, 84vw);
  z-index: 99;
  display: flex;
  flex-direction: column;
  padding: 20px 16px 24px;
  background: var(--color-ink);
  border-right: 1px solid #232726;
  overflow-y: auto;
  transform: translateX(-102%);
  visibility: hidden;
  transition: transform var(--dur) var(--ease), visibility var(--dur) var(--ease);
}
.site-header[data-open] .nav-shell { transform: translateX(0); visibility: visible; }

.primary-nav { flex: 1; }
.nav-list { display: flex; flex-direction: column; }
.nav-item { border-bottom: 1px solid #232726; }
.nav-item:first-child { border-top: 1px solid #232726; }

.nav-link {
  position: relative;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 10px;
  color: var(--color-fog);
  transition: color var(--dur) var(--ease), background var(--dur) var(--ease);
}
.nav-link:hover { color: var(--color-paper); background: rgba(255, 255, 255, 0.04); }
.nav-link[aria-current="page"] { color: var(--color-paper); background: rgba(255, 255, 255, 0.06); }
.nav-link[aria-current="page"]::before { content: ""; position: absolute; left: 0; top: 9px; bottom: 9px; width: 3px; background: var(--color-spring); }

.nav-index { font-family: var(--font-mono); font-size: 12px; color: #6f7370; letter-spacing: 0.05em; }
.nav-text { font-family: var(--font-serif); font-size: 16px; letter-spacing: 0.14em; }

.nav-mark {
  margin-left: auto;
  display: grid;
  place-items: center;
  width: 24px;
  height: 24px;
  font-family: var(--font-serif);
  font-size: 14px;
  color: var(--color-fog);
  border: 1px solid #3a3f3d;
}
.nav-mark-spring { color: var(--color-spring); border-color: rgba(13, 143, 90, 0.4); }
.nav-mark-summer { color: var(--color-summer); border-color: rgba(29, 111, 184, 0.4); }
.nav-mark-autumn { color: var(--color-autumn); border-color: rgba(217, 119, 46, 0.4); }
.nav-mark-winter { color: var(--color-winter); border-color: rgba(232, 239, 237, 0.4); }
.nav-mark-access { color: var(--color-tea); border-color: rgba(169, 122, 80, 0.5); }

.rail-note {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 20px 4px 8px;
  border-top: 1px solid #232726;
  writing-mode: vertical-rl;
  text-orientation: mixed;
  font-family: var(--font-serif);
  font-size: 13px;
  letter-spacing: 0.28em;
  color: var(--color-fog);
}
.rail-seal { font-size: 12px; letter-spacing: 0.22em; color: var(--color-tea); border: 1px solid var(--color-tea); padding: 6px 3px; }

/* ---------- 5. 站内检索 ---------- */
.header-search {
  position: fixed;
  top: var(--topbar-h);
  left: 0;
  right: 0;
  height: var(--search-h);
  z-index: 98;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 0 16px;
  background: var(--color-paper);
  border-bottom: 1px solid var(--color-fog);
}

.search-icon {
  position: relative;
  width: 14px;
  height: 14px;
  border: 2px solid var(--color-muted);
  border-radius: 50%;
  flex-shrink: 0;
}
.search-icon::after { content: ""; position: absolute; right: -6px; bottom: -4px; width: 7px; height: 2px; background: var(--color-muted); transform: rotate(45deg); }

.search-input {
  flex: 1;
  min-width: 0;
  padding: 8px 2px;
  border: 0;
  border-bottom: 1px solid var(--color-fog);
  border-radius: 0;
  background: transparent;
  color: var(--color-line);
  font-size: 14px;
  appearance: none;
}
.search-input::placeholder { color: var(--color-fog); }
.search-input:focus { outline: none; border-bottom-color: var(--color-spring); }
.search-clear { width: 24px; height: 24px; display: grid; place-items: center; color: var(--color-muted); font-size: 18px; line-height: 1; }
.search-clear:hover { color: var(--color-line); }

/* ---------- 6. 阅读进度条 ---------- */
.scroll-progress { position: fixed; top: 0; left: 0; right: 0; height: 3px; z-index: 500; pointer-events: none; }
.scroll-progress span { display: block; width: 100%; height: 100%; background: var(--color-spring); transform-origin: left center; transform: scaleX(0); }

/* ---------- 7. 主体偏移 ---------- */
#main-content { padding-top: calc(var(--topbar-h) + var(--search-h)); }

/* ---------- 8. 页脚 ---------- */
.site-footer { background: var(--color-ink); color: var(--color-fog); font-size: 14px; line-height: 1.8; }
.site-footer::before { content: ""; display: block; height: 3px; background: linear-gradient(90deg, var(--color-spring) 0%, var(--color-spring) 25%, var(--color-summer) 25%, var(--color-summer) 50%, var(--color-autumn) 50%, var(--color-autumn) 75%, var(--color-winter) 75%, var(--color-winter) 100%); }

.footer-inner { width: min(var(--container), 100%); margin-inline: auto; padding: 48px clamp(20px, 4vw, 48px) 24px; }
.footer-cols { display: grid; grid-template-columns: 1fr; gap: 36px; padding-bottom: 36px; border-bottom: 1px solid #232726; }
.footer-col { min-width: 0; }

.footer-kicker { font-family: var(--font-mono); font-size: 11px; letter-spacing: 0.22em; color: #6f7370; margin-bottom: 10px; }
.footer-brand-title { font-size: 24px; letter-spacing: 0.1em; color: var(--color-paper); margin-bottom: 10px; }
.footer-brand-title span { font-size: 13px; color: var(--color-spring); margin-left: 8px; letter-spacing: 0.14em; }
.footer-desc { font-size: 13px; color: #a0a5a2; max-width: 360px; }
.footer-cycle { margin-top: 14px; font-family: var(--font-serif); font-size: 15px; letter-spacing: 0.35em; color: var(--color-tea); }

.footer-heading { font-family: var(--font-serif); font-size: 15px; letter-spacing: 0.16em; color: var(--color-paper); padding-bottom: 10px; margin-bottom: 12px; border-bottom: 1px solid #232726; }

.footer-link-list li + li { margin-top: 6px; }
.footer-link-list a { font-size: 13px; color: var(--color-fog); transition: color var(--dur) var(--ease), padding-left var(--dur) var(--ease); }
.footer-link-list a:hover { color: var(--color-spring); padding-left: 4px; }

.footer-contact-list li { padding: 8px 0; border-bottom: 1px solid #1c201e; font-size: 13px; word-break: break-all; }
.footer-contact-list .contact-label { display: block; font-family: var(--font-mono); font-size: 11px; letter-spacing: 0.14em; color: #6f7370; margin-bottom: 2px; }

.footer-meta { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 10px; padding-top: 18px; font-size: 12px; color: #6f7370; }
.footer-icp { font-family: var(--font-mono); letter-spacing: 0.06em; }

/* ---------- 9. 返回顶部 ---------- */
.back-to-top {
  position: fixed;
  right: 20px;
  bottom: 24px;
  z-index: 90;
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  background: var(--color-ink);
  color: var(--color-paper);
  border: 1px solid var(--color-line);
  font-size: 18px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease), visibility var(--dur) var(--ease), background var(--dur) var(--ease), border-color var(--dur) var(--ease);
}
.back-to-top.is-visible { opacity: 1; visibility: visible; transform: none; }
.back-to-top:hover { background: var(--color-spring); border-color: var(--color-spring); color: #fff; }

/* ---------- 10. 面包屑 ---------- */
.breadcrumb { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; font-size: 13px; color: var(--color-muted); margin-bottom: 24px; }
.breadcrumb a { color: var(--color-muted); transition: color var(--dur) var(--ease); }
.breadcrumb a:hover { color: var(--color-spring); }
.breadcrumb-sep { color: var(--color-fog); font-family: var(--font-mono); font-size: 12px; }

/* ---------- 11. 章节标题 ---------- */
.section-head { display: flex; align-items: flex-start; gap: 18px; margin-bottom: 32px; }
.section-anno {
  writing-mode: vertical-rl;
  text-orientation: mixed;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.3em;
  color: var(--color-muted);
  padding-top: 8px;
  border-top: 1px solid var(--color-fog);
}
.section-title { font-size: clamp(28px, 4vw, 44px); letter-spacing: 0.05em; }

/* ---------- 12. 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 22px;
  border: 1px solid var(--color-line);
  background: transparent;
  color: var(--color-line);
  font-size: 14px;
  letter-spacing: 0.1em;
  line-height: 1.4;
  transition: background var(--dur) var(--ease), color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}
.btn:hover { background: var(--color-line); color: var(--color-paper); }
.btn-primary { background: var(--color-spring); border-color: var(--color-spring); color: #fff; }
.btn-primary:hover { background: #0b7a4c; border-color: #0b7a4c; }
.btn-outline { border-color: var(--color-fog); color: var(--color-muted); }
.btn-outline:hover { border-color: var(--color-line); color: var(--color-line); background: transparent; }

/* ---------- 13. 标签 ---------- */
.tag { display: inline-block; padding: 3px 10px; font-family: var(--font-mono); font-size: 12px; letter-spacing: 0.08em; border: 1px solid currentColor; line-height: 1.5; }
.tag-spring { color: var(--color-spring); }
.tag-summer { color: var(--color-summer); }
.tag-autumn { color: var(--color-autumn); }
.tag-winter { color: var(--color-muted); background: var(--color-winter); border-color: var(--color-winter); }
.tag-tea { color: var(--color-tea); }

/* ---------- 14. 卡片 ---------- */
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 20px; }
.card { position: relative; padding: 24px; background: #fff; border: 1px solid var(--color-fog); transition: border-color var(--dur) var(--ease), transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease); }
.card:hover { border-color: var(--color-line); transform: translateY(-2px); box-shadow: 0 8px 20px rgba(0, 0, 0, 0.04); }
.card h3, .card h4 { margin-bottom: 8px; }
.card p { color: var(--color-muted); font-size: 14px; }
.card-spring { border-top: 3px solid var(--color-spring); }
.card-summer { border-top: 3px solid var(--color-summer); }
.card-autumn { border-top: 3px solid var(--color-autumn); }
.card-winter { border-top: 3px solid var(--color-winter); }

/* ---------- 15. 图片容器 ---------- */
.image-frame { position: relative; overflow: hidden; background: var(--color-winter); border: 1px solid var(--color-fog); }
.image-frame::before { content: ""; display: block; padding-top: 56.25%; }
.image-frame > img,
.image-frame > .image-placeholder { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; }
.image-frame--portrait::before { padding-top: 125%; }
.image-frame--square::before { padding-top: 100%; }
.image-frame--panorama::before { padding-top: 45%; }

/* ---------- 16. 表格 ---------- */
.table-wrap { overflow-x: auto; border: 1px solid var(--color-fog); background: #fff; }
.table-wrap table { width: 100%; border-collapse: collapse; font-size: 14px; }
.table-wrap th, .table-wrap td { padding: 10px 14px; border-bottom: 1px solid var(--color-fog); text-align: left; vertical-align: top; }
.table-wrap th { background: var(--color-winter); font-family: var(--font-serif); font-weight: 700; white-space: nowrap; }
.table-wrap tr:last-child td { border-bottom: 0; }

/* ---------- 17. FAQ ---------- */
.faq-list { border-top: 1px solid var(--color-fog); }
.faq-item { border-bottom: 1px solid var(--color-fog); }
.faq-question { display: flex; align-items: center; justify-content: space-between; gap: 16px; width: 100%; padding: 18px 8px; text-align: left; font-family: var(--font-serif); font-size: 17px; color: var(--color-line); }
.faq-question:hover { color: var(--color-spring); }
.faq-icon { position: relative; width: 14px; height: 14px; flex-shrink: 0; }
.faq-icon::before, .faq-icon::after { content: ""; position: absolute; background: var(--color-spring); transition: transform var(--dur) var(--ease); }
.faq-icon::before { top: 6px; left: 0; width: 14px; height: 2px; }
.faq-icon::after { top: 0; left: 6px; width: 2px; height: 14px; }
.faq-item[data-open] .faq-icon::after { transform: scaleY(0); }
.faq-answer { max-height: 0; overflow: hidden; transition: max-height var(--dur) var(--ease); }
.faq-item[data-open] .faq-answer { max-height: 600px; }
.faq-answer-inner { padding: 0 8px 20px; color: var(--color-muted); font-size: 15px; }

/* ---------- 18. 章节目录 Scroll Spy ---------- */
.toc { border: 1px solid var(--color-fog); background: var(--color-winter); padding: 12px; margin-bottom: 28px; }
.toc-title { display: flex; align-items: baseline; gap: 8px; font-family: var(--font-serif); font-size: 15px; letter-spacing: 0.1em; padding: 6px 8px 10px; border-bottom: 1px solid var(--color-fog); margin-bottom: 8px; }
.toc-title::before { content: "目"; writing-mode: vertical-rl; font-family: var(--font-mono); font-size: 12px; color: var(--color-spring); }
.toc a { display: block; padding: 8px 10px; color: var(--color-muted); font-size: 14px; border-left: 2px solid transparent; transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease), background var(--dur) var(--ease); }
.toc a:hover { color: var(--color-line); background: rgba(255, 255, 255, 0.6); }
.toc a.is-active { color: var(--color-line); border-left-color: var(--color-spring); font-weight: 600; background: rgba(255, 255, 255, 0.8); }

/* ---------- 19. 检索高亮 ---------- */
mark.search-hit { background: transparent; color: inherit; border-bottom: 2px solid var(--color-spring); padding: 0 2px; }
mark.search-hit.is-current { background: var(--color-spring); color: #fff; border-bottom-color: var(--color-spring); }

/* ---------- 20. 滚动显现 ---------- */
.js [data-reveal] { opacity: 0; transform: translateY(14px); transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease); }
.js [data-reveal].is-revealed { opacity: 1; transform: none; }

/* ---------- 21. 平板与桌面框架 ---------- */
@media (min-width: 768px) {
  .footer-cols { grid-template-columns: 1.2fr 1fr 1.3fr; gap: 40px; }
  .brand-mark { width: 38px; height: 38px; }
  .brand-cn { font-size: 22px; }
  .brand-sub { font-size: 11px; }
}

@media (min-width: 1100px) {
  .site-header {
    right: auto;
    bottom: 0;
    width: var(--header-w);
    height: auto;
    display: flex;
    flex-direction: column;
    border-right: 1px solid #232726;
  }

  .header-bar {
    height: auto;
    flex-direction: column;
    align-items: flex-start;
    gap: 18px;
    padding: 28px 24px 22px;
    border-bottom: 1px solid #232726;
  }

  .brand { flex-direction: column; align-items: flex-start; gap: 8px; }
  .brand-mark { width: 46px; height: 46px; }
  .brand-mark::before { inset: 6px; font-size: 16px; }
  .brand-cn { font-size: 26px; }
  .brand-sub { font-size: 11px; }

  .nav-toggle { display: none; }

  .nav-shell {
    position: static;
    transform: none;
    visibility: visible;
    width: auto;
    flex: 1;
    padding: 24px 14px 12px;
    border-right: 0;
    background: transparent;
    overflow-y: auto;
  }

  .nav-item:first-child { border-top: 0; }
  .nav-link { padding: 13px 10px; }
  .nav-link[aria-current="page"]::before { top: 10px; bottom: 10px; }
  .rail-note { padding: 18px 6px 10px; }

  .header-search {
    top: 0;
    left: var(--header-w);
    right: 0;
    height: var(--topbar-h);
    justify-content: flex-end;
  }
  .header-search .search-input { flex: 0 1 360px; }

  #main-content { margin-left: var(--header-w); padding-top: var(--topbar-h); }
  .site-footer { margin-left: var(--header-w); }
}

/* ---------- 22. 动效与无障碍 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  .js [data-reveal] { opacity: 1; transform: none; }
  .back-to-top { transform: none; }
}