/* ============================================================
   高中数学站 · 主题样式
   风格来源 note.minims.cn（halo-theme-cosolar 极简笔记）
   设计规范见 design-spec.md
   ============================================================ */

:root {
  --color-primary: #10b981;
  --color-primary-hover: #059669;
  --color-primary-light: #34d399;
  --color-primary-bg: #ecfdf5;
  --color-primary-border: #a7f3d0;

  --color-bg: #f8fafc;
  --color-card: #fff;
  --color-card-hover: #f8fafc;
  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-text-muted: #94a3b8;
  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;
  --color-dark: #0f172a;

  --container-max: 1600px;
  --header-height: 64px;
  --sidebar-width: 380px;
  --toc-width: 240px;
  --content-gap: 24px;

  --radius-xl: 20px;
  --radius-lg: 16px;
  --radius-md: 10px;
  --radius-sm: 6px;
  --radius-full: 9999px;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, .04);
  --shadow: 0 1px 3px rgba(0, 0, 0, .08);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, .08);
  --shadow-hover: 0 8px 25px -5px rgba(0, 0, 0, .12);

  --transition: .2s ease;

  /* 字体对齐 sslu.cn：系统原生中英文字体栈，清晰锐利（不加载任何中文 webfont） */
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", Consolas, monospace;
}

[data-theme="dark"] {
  --color-primary: #10b981;
  --color-primary-hover: #34d399;
  --color-primary-light: #6ee7b7;
  --color-primary-bg: rgba(16, 185, 129, .10);
  --color-primary-border: rgba(16, 185, 129, .30);

  --color-bg: #0f172a;
  --color-card: #1e293b;
  --color-card-hover: #334155;
  --color-text: #f1f5f9;
  --color-text-secondary: #94a3b8;
  --color-text-muted: #64748b;
  --color-border: #334155;
  --color-border-light: #263243;
  --color-dark: #f1f5f9;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, .2);
  --shadow: 0 1px 3px rgba(0, 0, 0, .3);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, .3);
  --shadow-hover: 0 8px 25px -5px rgba(0, 0, 0, .4);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; overflow-x: hidden; }

body {
  font-family: var(--font-sans);
  font-size: 15px;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-bg);
  transition: background-color var(--transition), color var(--transition);
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
}

a { color: var(--color-primary); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--color-primary-hover); }
img { max-width: 100%; height: auto; display: block; }
ul, ol { list-style: none; }
button { cursor: pointer; background: none; border: none; font: inherit; color: inherit; }

::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-thumb { background: rgba(16, 185, 129, .45); border-radius: 9999px; }
::-webkit-scrollbar-thumb:hover { background: rgba(16, 185, 129, .75); }

.container { max-width: var(--container-max); margin: 0 auto; padding: 0 20px; }

/* ---------- 顶部 ---------- */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: color-mix(in srgb, var(--color-card) 85%, transparent);
  -webkit-backdrop-filter: blur(12px); backdrop-filter: blur(12px);
  border-bottom: 1px solid color-mix(in srgb, var(--color-border) 60%, transparent);
  transition: box-shadow var(--transition);
}
.site-header.scrolled { box-shadow: 0 1px 12px rgba(0, 0, 0, .06); }

.header-inner {
  height: var(--header-height);
  display: flex; align-items: center; justify-content: space-between; gap: 24px;
}
.header-logo { display: flex; align-items: center; gap: 10px; flex-shrink: 0; }
.header-logo:hover { opacity: .85; }
.logo-icon {
  width: 36px; height: 36px; border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-hover));
  color: #fff; font-family: var(--font-mono); font-size: 16px; font-weight: 700;
  display: flex; align-items: center; justify-content: center;
  box-shadow: 0 2px 8px color-mix(in srgb, var(--color-primary) 30%, transparent);
}
.logo-text { display: flex; flex-direction: column; line-height: 1.3; }
.logo-name { color: var(--color-text); font-size: 17px; font-weight: 700; letter-spacing: .5px; }
.logo-tagline { color: var(--color-text-muted); font-size: 11px; letter-spacing: .3px; white-space: nowrap; }

.header-nav { flex: 1; display: flex; align-items: center; gap: 2px; margin-left: 8px; }
.header-nav a {
  color: var(--color-text); font-size: 14px; letter-spacing: .8px;
  padding: 7px 14px; border-radius: var(--radius-full);
  transition: all var(--transition); white-space: nowrap;
}
.header-nav a:hover { color: var(--color-primary); background: var(--color-primary-bg); }
.header-nav a.active { color: var(--color-primary); background: var(--color-primary-bg); font-weight: 600; }

.header-actions { display: flex; align-items: center; gap: 6px; flex-shrink: 0; }
.icon-btn {
  width: 34px; height: 34px; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  color: var(--color-text-secondary); transition: all var(--transition);
}
.icon-btn:hover { color: var(--color-primary); background: var(--color-primary-bg); }
.icon-btn svg { width: 18px; height: 18px; }
.menu-toggle { display: none; }

/* ---------- 布局 ---------- */
.site-main { padding: 28px 0 32px; }
.layout-grid {
  display: grid; grid-template-columns: minmax(0, 1fr) var(--sidebar-width);
  gap: var(--content-gap); align-items: start;
}
.content-area { min-width: 0; }

/* 内容页三栏：左侧动作条 56px / 正文 / 右侧目录 240px（与模板站一致，无侧栏） */
.post-layout {
  display: grid; grid-template-columns: 56px minmax(0, 1fr) var(--toc-width);
  gap: var(--content-gap); align-items: start;
}
.post-actions { position: sticky; top: 88px; display: flex; flex-direction: column; gap: 10px; align-items: center; }
.post-actions .action-btn {
  width: 40px; height: 40px; border-radius: 50%; display: flex; align-items: center; justify-content: center;
  background: var(--color-card); border: 1px solid var(--color-border); color: var(--color-text-secondary);
  transition: all var(--transition);
}
.post-actions .action-btn:hover { color: var(--color-primary); border-color: var(--color-primary-border); background: var(--color-primary-bg); }
.post-actions .action-btn svg { width: 18px; height: 18px; }
.reading-progress { width: 40px; height: 3px; border-radius: 2px; background: var(--color-border-light); overflow: hidden; }
.reading-progress i { display: block; height: 100%; width: 0; background: var(--color-primary); transition: width .1s linear; }

.post-toc { position: sticky; top: 88px; max-height: calc(100vh - 120px); overflow-y: auto; padding-left: 14px; border-left: 1px solid var(--color-border-light); }
.post-toc .toc-title { font-size: 13px; font-weight: 700; color: var(--color-text); margin-bottom: 10px; letter-spacing: .5px; }
.post-toc a {
  display: block; font-size: 13px; line-height: 1.6; color: var(--color-text-secondary);
  padding: 4px 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
  border-left: 2px solid transparent; padding-left: 10px; margin-left: -15px;
}
.post-toc a:hover { color: var(--color-primary); }
.post-toc a.active { color: var(--color-primary); border-left-color: var(--color-primary); font-weight: 600; }
.post-toc a.lv3 { padding-left: 22px; font-size: 12px; opacity: .85; }
.post-toc .toc-info { margin-bottom: 12px; }
.post-toc .toc-info div {
  display: flex; align-items: baseline; justify-content: space-between; gap: 8px;
  padding: 5px 0; border-bottom: 1px dashed var(--color-border-light); font-size: 13px;
}
.post-toc .toc-info span { color: var(--color-text-muted); flex-shrink: 0; }
.post-toc .toc-info b { color: var(--color-text); font-weight: 600; text-align: right; }
.post-toc .toc-back {
  display: block; text-align: center; font-size: 13px; color: var(--color-primary);
  border: 1px solid var(--color-primary-border); background: var(--color-primary-bg);
  border-radius: var(--radius-md); padding: 7px 0; margin-top: 4px; white-space: normal;
}
.post-toc .toc-back:hover { background: var(--color-primary); color: #fff; }

/* ---------- 首页/栏目页 精选轮播 ---------- */
.featured-carousel {
  position: relative; overflow: hidden; border-radius: var(--radius-lg);
  margin-bottom: 28px; border: 1px solid var(--color-border); background: var(--color-card);
}
.carousel-track { position: relative; }
.featured-carousel .carousel-slide { display: none; }
.featured-carousel .carousel-slide.active { display: block; }
.featured-card {
  position: relative; min-height: 340px; display: flex; align-items: flex-end; overflow: hidden;
}
.featured-bg { position: absolute; inset: 0; background-size: cover; background-position: center; }
.featured-bg::after { content: ""; position: absolute; inset: 0; background: linear-gradient(90deg, rgba(10,20,35,.82) 0%, rgba(10,20,35,.45) 55%, rgba(10,20,35,.15) 100%); }
.featured-content { position: relative; z-index: 2; padding: 34px 38px; max-width: 78%; color: #fff; }
.featured-badge {
  display: inline-block; background: var(--color-primary); color: #fff; font-size: 12px; font-weight: 600;
  padding: 3px 10px; border-radius: var(--radius-full); margin-bottom: 12px;
}
.featured-title { font-size: 26px; font-weight: 700; line-height: 1.35; margin-bottom: 10px; }
.featured-title a { color: #fff; }
.featured-title a:hover { color: #fff; text-decoration: underline; }
.featured-desc {
  font-size: 14px; line-height: 1.7; color: rgba(255,255,255,.82); margin-bottom: 14px;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden;
}
.featured-meta { display: flex; align-items: center; gap: 16px; font-size: 12px; color: rgba(255,255,255,.7); flex-wrap: wrap; }
.featured-meta .btn-sm {
  background: var(--color-primary); color: #fff; padding: 5px 14px; border-radius: var(--radius-full);
  font-size: 12px; font-weight: 600;
}
.featured-meta .btn-sm:hover { background: var(--color-primary-hover); color: #fff; }
.carousel-dots { position: absolute; right: 18px; bottom: 18px; z-index: 3; display: flex; gap: 7px; }
.carousel-dots button { width: 8px; height: 8px; border-radius: 50%; background: rgba(255,255,255,.45); transition: all var(--transition); }
.carousel-dots button.active { background: #fff; width: 22px; border-radius: 4px; }

/* ---------- 栏目头 ---------- */
.page-head {
  background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: var(--radius-lg); box-shadow: var(--shadow-sm);
  padding: 24px 28px; margin-bottom: 20px;
}
.page-head h1 { font-size: 22px; font-weight: 700; color: var(--color-text); margin-bottom: 6px; }
.page-head p { color: var(--color-text-secondary); font-size: 14px; }
.page-head .stat { color: var(--color-primary); font-weight: 600; }

.section-title {
  display: flex; align-items: baseline; gap: 10px; margin: 8px 0 14px;
  font-size: 18px; font-weight: 700; color: var(--color-text);
}
.section-title small { font-size: 12px; font-weight: 500; color: var(--color-text-muted); }

/* ---------- 文章卡 ---------- */
.article-list { display: flex; flex-direction: column; }
.article-card {
  background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: var(--radius-lg); padding: 20px; margin-bottom: 12px;
  display: flex; gap: 18px; align-items: stretch;
  transition: all var(--transition);
}
.article-card:hover {
  border-color: var(--color-primary-border); box-shadow: var(--shadow-hover);
  transform: translateY(-2px);
}
.article-thumb {
  width: 230px; flex-shrink: 0; border-radius: var(--radius-md);
  background: var(--color-border-light); overflow: hidden;
  display: flex; align-items: center; justify-content: center; position: relative;
}
.article-thumb img { width: 100%; height: 100%; object-fit: cover; }
.thumb-ph { font-size: 40px; font-family: var(--font-mono); color: var(--color-primary); opacity: .35; }
.article-body { display: flex; flex-direction: column; gap: 6px; min-width: 0; flex: 1; }
.article-card-title {
  color: var(--color-text); font-size: 16px; font-weight: 600; line-height: 1.5;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden;
}
.article-card:hover .article-card-title { color: var(--color-primary); }
.article-card-excerpt {
  color: var(--color-text-secondary); font-size: 13px; line-height: 1.6;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden;
}
.article-card-tags { display: flex; flex-wrap: wrap; gap: 6px; }
.tag {
  color: var(--color-primary); background: var(--color-primary-bg);
  border-radius: var(--radius-full); padding: 3px 10px; font-size: 12px; font-weight: 500;
  display: inline-flex; align-items: center; transition: all var(--transition);
}
.tag:hover { background: var(--color-primary); color: #fff; }
.article-card-meta {
  color: var(--color-text-muted); font-size: 12px; margin-top: auto;
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
}
.meta-item { display: inline-flex; align-items: center; gap: 4px; }
.meta-item svg { width: 13px; height: 13px; opacity: .8; }

/* ---------- 分页 ---------- */
.pagination { display: flex; align-items: center; justify-content: center; gap: 6px; margin-top: 24px; flex-wrap: wrap; }
.pagination a, .pagination button, .pagination span {
  min-width: 34px; height: 34px; padding: 0 10px; border-radius: var(--radius-md);
  display: inline-flex; align-items: center; justify-content: center;
  font-size: 13px; color: var(--color-text-secondary); background: var(--color-card);
  border: 1px solid var(--color-border); transition: all var(--transition); cursor: pointer;
}
.pagination a:hover, .pagination button:hover { color: var(--color-primary); border-color: var(--color-primary-border); background: var(--color-primary-bg); }
.pagination .current { background: var(--color-primary); color: #fff; border-color: var(--color-primary); font-weight: 600; }
.pagination .disabled { opacity: .4; pointer-events: none; }

/* ---------- 侧栏 ---------- */
.sidebar { display: flex; flex-direction: column; gap: 20px; }
.widget {
  background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: var(--radius-lg); box-shadow: var(--shadow-sm); padding: 20px;
}
.widget-title {
  display: flex; align-items: center; gap: 8px; margin-bottom: 14px;
  font-size: 14px; font-weight: 600; color: var(--color-text);
}
.widget-title svg { width: 16px; height: 16px; color: var(--color-primary); }
.widget p { font-size: 13px; color: var(--color-text-secondary); line-height: 1.7; }

.search-box { position: relative; }
.search-box input {
  width: 100%; height: 40px; padding: 0 14px 0 38px;
  border: 1px solid var(--color-border); border-radius: var(--radius-md);
  background: var(--color-bg); color: var(--color-text); font-size: 14px;
  transition: all var(--transition);
}
.search-box input:focus {
  outline: none; border-color: var(--color-primary);
  background: var(--color-card); box-shadow: 0 0 0 3px var(--color-primary-bg);
}
.search-box svg { position: absolute; left: 13px; top: 12px; width: 16px; height: 16px; color: var(--color-text-muted); }

.cat-list { display: flex; flex-direction: column; gap: 4px; }
.cat-list a {
  display: flex; align-items: center; justify-content: space-between;
  padding: 8px 10px; border-radius: var(--radius-md); font-size: 14px;
  color: var(--color-text-secondary); transition: all var(--transition);
}
.cat-list a:hover { background: var(--color-primary-bg); color: var(--color-primary); }
.cat-list a.active { background: var(--color-primary); color: #fff; font-weight: 500; }
.cat-list .count {
  font-size: 11px; background: var(--color-border-light); color: var(--color-text-muted);
  padding: 1px 8px; border-radius: var(--radius-full);
}
.cat-list a.active .count { background: rgba(255, 255, 255, .25); color: #fff; }

.widget-list li { border-bottom: 1px solid var(--color-border-light); }
.widget-list li:last-child { border-bottom: none; }
.widget-list a {
  display: block; padding: 9px 0; font-size: 13px; color: var(--color-text-secondary);
  line-height: 1.5; transition: color var(--transition);
  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
.widget-list a:hover { color: var(--color-primary); }

.tag-cloud { display: flex; flex-wrap: wrap; gap: 6px; }

.stat-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.stat-cell {
  background: var(--color-primary-bg); border-radius: var(--radius-lg);
  padding: 12px 8px; text-align: center;
}
.stat-cell .num { font-size: 20px; font-weight: 800; color: var(--color-text); line-height: 1.2; font-variant-numeric: tabular-nums; }
.stat-cell .label { font-size: 11px; color: var(--color-text-muted); }

/* ---------- 文章页 ---------- */
.article-detail {
  background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: var(--radius-lg); box-shadow: var(--shadow-sm); padding: 40px;
}
.article-detail-title { font-size: 28px; font-weight: 700; line-height: 1.4; color: var(--color-text); margin-bottom: 14px; }
.article-detail-meta {
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
  font-size: 13px; color: var(--color-text-muted);
  padding-bottom: 18px; margin-bottom: 24px; border-bottom: 1px solid var(--color-border-light);
}
.article-detail-meta > span { display: inline-flex; align-items: center; gap: 5px; }
.article-detail-meta svg { width: 14px; height: 14px; flex-shrink: 0; opacity: .8; }
/* ================= 正文排版规范 ================= */
.prose {
  font-size: 16px; line-height: 1.85; color: var(--color-text);
  word-wrap: break-word; overflow-wrap: break-word;
  letter-spacing: .01em;
}
.prose > *:first-child { margin-top: 0; }
.prose > *:last-child { margin-bottom: 0; }

.prose p { margin: 0 0 1.05em; }
.prose p:empty, .prose p.blank { display: none; }

/* 标题层级 */
.prose h1, .prose h2, .prose h3, .prose h4 {
  color: var(--color-text); font-weight: 700; line-height: 1.45;
  scroll-margin-top: 88px;
}
.prose h1 { font-size: 1.55em; margin: 1.6em 0 .7em; }
.prose h2 {
  font-size: 1.32em; margin: 1.7em 0 .7em; padding-left: 12px;
  border-left: 4px solid var(--color-primary);
}
.prose h3 { font-size: 1.14em; margin: 1.5em 0 .6em; }
.prose h4 { font-size: 1.02em; margin: 1.4em 0 .5em; color: var(--color-text-secondary); }

/* 强调 */
.prose strong { font-weight: 700; color: var(--color-text); }
.prose em { font-style: normal; color: var(--color-primary); font-weight: 600; }
.prose a { text-decoration: underline; text-underline-offset: 2px; }

/* 图片：居中、限宽、统一间距（试题/教研页大量图片靠这条排版） */
.prose img {
  display: block; max-width: 100%; width: auto; height: auto;
  margin: 18px auto; border-radius: var(--radius-md);
  border: 1px solid var(--color-border-light); background: #fff;
}
.prose figure { margin: 20px 0; text-align: center; }
.prose figure img { margin: 0 auto; }
.prose figcaption {
  font-size: 13px; color: var(--color-text-muted); margin-top: 8px; text-align: center;
}
/* 段落里只有一张图时收紧上下间距，避免图片之间出现大片空白 */
.prose p.img-only { margin: 0 0 10px; }
.prose p.img-only img { margin: 0 auto; }

/* 列表 */
.prose ul, .prose ol { padding-left: 1.6em; margin: 0 0 1.05em; }
.prose ul { list-style: disc; }
.prose ol { list-style: decimal; }
.prose li { margin-bottom: .35em; }
.prose li > ul, .prose li > ol { margin: .35em 0 0; }

/* 引用 */
.prose blockquote {
  border-left: 3px solid var(--color-primary); background: var(--color-primary-bg);
  padding: 12px 18px; margin: 18px 0; border-radius: 0 var(--radius-md) var(--radius-md) 0;
  color: var(--color-text-secondary);
}
.prose blockquote p:last-child { margin-bottom: 0; }

/* 表格：窄屏可横向滚动 */
.prose .table-wrap { overflow-x: auto; margin: 18px 0; -webkit-overflow-scrolling: touch; }
.prose table { width: 100%; border-collapse: collapse; font-size: 15px; }
.prose th, .prose td { border: 1px solid var(--color-border); padding: 9px 12px; text-align: left; }
.prose th { background: var(--color-border-light); font-weight: 600; }

/* 代码 */
.prose pre {
  background: var(--color-dark); color: #e2e8f0; padding: 14px 16px;
  border-radius: var(--radius-md); overflow-x: auto; font-family: var(--font-mono); font-size: .85em;
  margin: 18px 0; line-height: 1.7;
}
.prose code { font-family: var(--font-mono); font-size: .88em; background: var(--color-border-light); padding: 2px 6px; border-radius: 4px; }
.prose pre code { background: none; padding: 0; font-size: 1em; }
.prose hr { border: none; border-top: 1px solid var(--color-border); margin: 28px 0; }

/* 公式（KaTeX） */
.prose .math-inline { display: inline-block; }
.prose .katex { font-size: 1.05em; }
.prose .katex-display { margin: 20px 0; overflow-x: auto; overflow-y: hidden; padding: 2px 0; }
.prose span.math:not(:has(.katex)) {
  font-family: var(--font-mono); font-size: .95em; color: var(--color-primary);
  background: var(--color-primary-bg); padding: 1px 6px; border-radius: 4px;
}

.post-nav { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin-top: 24px; }
.nav-card {
  background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: var(--radius-lg); padding: 16px 20px; transition: all var(--transition);
}
.nav-card:hover { border-color: var(--color-primary); box-shadow: var(--shadow); }
.nav-card .label { color: var(--color-text-muted); font-size: 12px; margin-bottom: 4px; }
.nav-card .title { color: var(--color-text); font-size: 14px; font-weight: 600; line-height: 1.5;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.nav-card.next { text-align: right; }

.source-tip {
  margin-top: 20px; padding: 12px 16px; border-radius: var(--radius-md);
  background: var(--color-primary-bg); border: 1px solid var(--color-primary-border);
  font-size: 12px; color: var(--color-text-secondary);
}
.source-tip a { font-weight: 600; }

/* ---------- 页脚 ---------- */
.site-footer {
  background: var(--color-card); border-top: 1px solid var(--color-border);
  margin-top: 20px; padding: 40px 0 24px;
}
.footer-brand { margin-bottom: 24px; }
.footer-brand .slogan { font-size: 17px; font-weight: 700; color: var(--color-text); margin-bottom: 4px; }
.footer-brand .desc { font-size: 13px; color: var(--color-text-muted); }
.footer-stats { display: flex; flex-wrap: wrap; gap: 28px; margin-bottom: 24px; }
.footer-stats .item .num { font-size: 18px; font-weight: 700; color: var(--color-text); font-variant-numeric: tabular-nums; }
.footer-stats .item .label { font-size: 12px; color: var(--color-text-muted); }
.footer-bottom {
  border-top: 1px solid var(--color-border-light); padding-top: 18px;
  display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap;
  font-size: 12px; color: var(--color-text-muted);
}
.footer-bottom a:hover { color: var(--color-primary); }

/* ---------- 回到顶部 ---------- */
.back-to-top {
  position: fixed; right: 26px; bottom: 32px; width: 42px; height: 42px;
  border-radius: 50%; background: var(--color-primary); color: #fff;
  display: flex; align-items: center; justify-content: center;
  box-shadow: var(--shadow-md); opacity: 0; pointer-events: none;
  transform: translateY(8px); transition: all var(--transition); z-index: 90;
}
.back-to-top.visible { opacity: 1; pointer-events: auto; transform: translateY(0); }
.back-to-top:hover { background: var(--color-primary-hover); }

.empty-tip {
  background: var(--color-card); border: 1px solid var(--color-border);
  border-radius: var(--radius-lg); padding: 48px 24px; text-align: center;
  color: var(--color-text-secondary); font-size: 14px;
}

/* ---------- 响应式 ---------- */
@media (max-width: 1400px) {
  /* 目录栏在中等屏收窄，正文优先 */
  .post-layout { grid-template-columns: 56px minmax(0, 1fr) 200px; }
}
@media (max-width: 1200px) {
  .post-layout { grid-template-columns: 1fr; }
  .post-actions { position: static; flex-direction: row; justify-content: flex-start; order: 2; }
  .post-toc { display: none; }
}
@media (max-width: 1024px) {
  .layout-grid { grid-template-columns: 1fr; }
  .sidebar { flex-direction: row; flex-wrap: wrap; }
  .widget { flex: 1 1 300px; }
  .featured-card { min-height: 280px; }
  .featured-content { padding: 26px 28px; max-width: 88%; }
  .featured-title { font-size: 22px; }
}
@media (max-width: 768px) {
  .header-nav { display: none; }
  .menu-toggle { display: flex; }
  .header-nav.open {
    display: flex; flex-direction: column; align-items: stretch;
    position: absolute; top: var(--header-height); left: 0; right: 0;
    background: var(--color-card); border-bottom: 1px solid var(--color-border);
    padding: 8px 20px 14px; box-shadow: var(--shadow-md);
  }
  .header-nav.open a { padding: 10px 12px; }
  .article-card { gap: 10px; padding: 12px; }
  .article-thumb { width: 90px; height: 90px; align-self: flex-start; }
  .article-card-title { font-size: 15px; }
  .article-detail { padding: 22px 18px; }
  .article-detail-title { font-size: 21px; }
  .post-nav { grid-template-columns: 1fr; }
  .nav-card.next { text-align: left; }
  .footer-bottom { justify-content: center; text-align: center; }
  .featured-card { min-height: 240px; }
  .featured-content { padding: 20px 22px; max-width: 100%; }
  .featured-title { font-size: 19px; }
  .featured-desc { -webkit-line-clamp: 2; }
  .prose { font-size: 15px; }
}
@media (max-width: 480px) {
  .article-detail-title { font-size: 19px; }
  .prose h2 { font-size: 1.18em; }
}