/* ── 流形上的涂鸦 ── 数学笔记 ── */

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

:root {
  --bg:         #FAF9F5;
  --bg-card:    #FFFFFF;
  --bg-code:    #2D2D2D;
  --fg:         #1A1A1A;
  --fg-sec:     #555249;
  --fg-muted:   #9C978B;
  --accent:     #FEB246;
  --accent-dark:#D4922A;
  --border:     #E6E3DA;
  --rail:       rgba(230, 227, 218, 0.88);
  --serif:      "Source Serif 4", "Noto Serif SC", "Songti SC", Georgia, "Times New Roman", serif;
  --sans:       -apple-system, "Helvetica Neue", "PingFang SC", sans-serif;
  --mono:       "JetBrains Mono", "Fira Code", Consolas, monospace;
  --content-w:  760px;
}

@import url('https://fonts.googleapis.com/css2?family=Source+Serif+4:ital,opsz,wght@0,8..60,300..700;1,8..60,300..700&display=swap');

body {
  font-family: var(--serif);
  font-size: 17px;
  line-height: 1.8;
  color: var(--fg);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

/* ══════════════════════════════════════════════
   首页 Hero
   ══════════════════════════════════════════════ */
.hero {  position: relative;
  z-index: 1;  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 78vh;
  text-align: center;
  padding: 2rem;
}
.hero-title {
  font-size: 4.2rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin-bottom: 0.8rem;
}
.hero-subtitle {
  font-size: 1.25rem;
  color: var(--fg-sec);
  font-style: italic;
  margin-bottom: 2.5rem;
  line-height: 1.6;
  max-width: 500px;
}

/* 社交链接 — 一行排列 */
.hero-links {
  display: flex;
  gap: 1.2rem;
  align-items: center;
  flex-wrap: wrap;
  justify-content: center;
}
.hero-links a {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  color: var(--fg-muted);
  text-decoration: none;
  font-size: 0.88rem;
  font-family: var(--sans);
  transition: color 0.15s;
}
.hero-links a:hover { color: var(--fg); }
.hero-links svg { width: 16px; height: 16px; fill: currentColor; flex-shrink: 0; }
.hero-links .sep { color: var(--border); font-size: 0.7rem; user-select: none; }
/* 主博客链接用强调色 */
.hero-links a.blog-link { color: var(--accent-dark); }
.hero-links a.blog-link:hover { color: var(--fg); }

/* ══════════════════════════════════════════════
   首页内容区 — 三栏
   ══════════════════════════════════════════════ */
.home-body {  position: relative;
  z-index: 1;  display: flex;
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 2rem 4rem;
  gap: 2.5rem;
  justify-content: center;
}

/* ── 左侧时间轴（竖线+节点） ── */
.sidebar-timeline {
  width: 90px;
  flex-shrink: 0;
  position: relative;
  border-right: 1px solid var(--rail);
}
/* 贯穿竖线由右边框实现 */
.tl-year {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--fg-sec);
  font-family: var(--sans);
  letter-spacing: 0.04em;
  padding: 0.8rem 0;
  text-align: right;
  padding-right: 1.2rem;
  position: relative;
}
/* 年份横线 */
.tl-year::after {
  content: '';
  position: absolute;
  right: 0;
  top: 50%;
  width: 12px;
  height: 1px;
  background: var(--fg-muted);
}
.tl-dot {
  display: block;
  text-align: right;
  padding: 0.75rem 0;
  padding-right: 1.2rem;
  font-size: 0.78rem;
  color: var(--fg-muted);
  font-family: var(--sans);
  font-variant-numeric: tabular-nums;
  position: relative;
  text-decoration: none;
}
/* 节点圆点 */
.tl-dot::after {
  content: '';
  position: absolute;
  right: -3px;
  top: 50%;
  transform: translateY(-50%);
  width: 7px;
  height: 7px;
  background: var(--bg);
  border: 1.5px solid var(--border);
  border-radius: 50%;
  transition: border-color 0.15s, background 0.15s;
}
.tl-dot:hover::after {
  border-color: var(--accent);
  background: var(--accent);
}

/* ── 中间文章预览（无卡片，平铺学术风） ── */
.post-entries {
  flex: 1;
  max-width: 660px;
  min-width: 0;
}
.post-entry {
  padding: 1.5rem 0;
  border-bottom: 1px solid var(--border);
  scroll-margin-top: 5rem;
}
.post-entry:first-child { padding-top: 0.5rem; }
.post-entry-title {
  font-size: 1.35rem;
  font-weight: 600;
  line-height: 1.35;
  margin-bottom: 0.25rem;
}
.post-entry-title a {
  color: var(--fg);
  text-decoration: none;
}
.post-entry-title a:hover { color: var(--accent-dark); }
.post-entry-meta {
  font-size: 0.82rem;
  color: var(--fg-muted);
  font-family: var(--sans);
  margin-bottom: 0.5rem;
  display: flex;
  align-items: center;
  gap: 0.6rem;
}
.post-entry-cat {
  font-size: 0.82rem;
  color: var(--accent-dark);
  text-decoration: none;
  border-bottom: 1px dashed transparent;
  transition: color 0.15s, border-color 0.15s;
}
.post-entry-cat:hover {
  color: var(--fg);
  border-bottom-color: var(--accent);
}
.post-entry-abstract {
  font-size: 0.95rem;
  color: var(--fg-sec);
  font-style: italic;
  margin-bottom: 0.35rem;
  line-height: 1.65;
}
.post-entry-excerpt {
  font-size: 0.9rem;
  color: var(--fg-muted);
  line-height: 1.65;
}
.post-entry-more {
  display: inline-block;
  margin-top: 0.5rem;
  font-size: 0.88rem;
  font-family: var(--sans);
  color: var(--accent-dark);
  text-decoration: none;
  border-bottom: 1px dashed var(--accent);
}
.post-entry-more:hover { border-bottom-style: solid; }

/* ── 右侧分类 ── */
.sidebar-cats {
  width: 90px;
  flex-shrink: 0;
  padding-top: 0;
  position: relative;
  padding-left: 1.2rem;
  text-align: left;
  border-left: 1px solid var(--rail);
}
/* 与时间线同构的竖线样式，仅位置在左侧，由左边框实现 */
.sidebar-cats-title {
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--fg-muted);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  font-family: var(--sans);
  margin-bottom: 0.8rem;
}
.sidebar-cats a {
  display: block;
  font-size: 0.88rem;
  color: var(--fg-sec);
  text-decoration: none;
  padding: 0.25rem 0;
  transition: color 0.15s;
  font-family: var(--sans);
}
.sidebar-cats a:hover { color: var(--accent-dark); }
.sidebar-cats .cat-count {
  font-size: 0.75rem;
  color: var(--fg-muted);
  margin-left: 0.2em;
}

/* ══════════════════════════════════════════════
   文章页
   ══════════════════════════════════════════════ */
.layout {  position: relative;
  z-index: 1;  max-width: var(--content-w);
  margin: 0 auto;
  padding: 4rem 2rem 3rem;
}
.post-header {
  text-align: center;
  margin-bottom: 3rem;
}
.post-header h1 {
  font-size: 2.4rem;
  font-weight: 700;
  line-height: 1.25;
  margin-bottom: 0.6rem;
  letter-spacing: -0.01em;
}
.post-meta {
  font-size: 0.92rem;
  color: var(--fg-sec);
  line-height: 1.8;
}
.post-meta .author { font-style: italic; }
.post-meta .category-label {
  display: inline;
  font-size: 0.82rem;
  color: var(--accent-dark);
  font-family: var(--sans);
  text-decoration: none;
  border-bottom: 1px dashed transparent;
  transition: color 0.15s, border-color 0.15s;
}
.post-meta .category-label:hover {
  color: var(--fg);
  border-bottom-color: var(--accent);
}
.post-abstract {
  margin: 1rem auto 0;
  max-width: 540px;
  font-size: 0.95rem;
  color: var(--fg-sec);
  text-align: center;
  font-style: italic;
  line-height: 1.7;
}

/* 正文排版 */
article h2 {
  font-size: 1.45rem;
  font-weight: 700;
  margin: 2.8rem 0 1rem;
  padding-bottom: 0.3rem;
}
article h3 { font-size: 1.15rem; font-weight: 600; margin: 2rem 0 0.8rem; }
article h4 { font-size: 1rem; font-weight: 600; margin: 1.5rem 0 0.5rem; }
article p { margin-bottom: 1.2rem; line-height: 1.75; }
article ul, article ol { margin: 0 0 1.2rem 1.5rem; }
article li { margin-bottom: 0.3rem; }
article blockquote {
  margin: 1.2rem 0;
  padding: 1rem 1.2rem;
  border-left: 3px solid var(--accent); color: var(--fg-sec);
  background: var(--bg-card); border-radius: 0 4px 4px 0;
}
article blockquote p { margin: 0; }
article hr { border: none; border-top: 1px solid var(--border); margin: 2rem 0; }
article a { color: var(--accent-dark); text-decoration: underline; text-underline-offset: 2px; }
article a:hover { text-decoration-thickness: 2px; }
article img { max-width: 100%; margin: 1.5rem 0; border-radius: 4px; }
article code { font-family: var(--mono); font-size: 0.86em; background: var(--bg-card); padding: 0.15em 0.4em; border-radius: 3px; }
article pre { background: var(--bg-code); color: #E5E1DB; padding: 1.2rem 1.4rem; border-radius: 6px; overflow-x: auto; margin: 1.5rem 0; line-height: 1.5; }
article pre code { background: none; padding: 0; color: inherit; font-size: 0.85em; }

/* 三线表 */
article table { width: 100%; border-collapse: collapse; margin: 1.5rem 0; font-size: 0.95rem; line-height: 1.6; }
article thead th { text-align: left; font-weight: 600; padding: 0.6rem 1rem; border-top: 2px solid var(--fg); border-bottom: 1px solid var(--fg); }
article tbody td { padding: 0.6rem 1rem; border-bottom: 1px solid var(--border); vertical-align: top; }
article tbody tr:last-child td { border-bottom: 2px solid var(--fg); }

/* KaTeX */
.katex-display {
  margin: 1.5rem 0;
  overflow-x: auto;
  overflow-y: hidden; /* 防止出现垂直滚动条 */
  padding: 1rem 0;    /* 增加垂直内边距以容纳高公式，防止被 hidden 裁剪 */
}

/* 行内公式含上/下标或 \overset 时，确保行高能容纳公式高度 */
article p .katex { line-height: 1.6; display: inline-block; }

/* ── 侧边目录 (fixed) ── */
.toc {
  position: fixed;
  top: 50%;
  transform: translateY(-50%);
  left: max(1.5rem, calc((100vw - var(--content-w)) / 2 - 255px));
  width: 210px;
  max-height: min(60vh, 480px);
  overflow-y: scroll;
  overflow-x: hidden;
  font-size: 0.92rem;
  text-align: left;
  padding-right: 0.7rem;
  border-right: 1px solid var(--border);
  overscroll-behavior: contain;
  scrollbar-width: none;
  scrollbar-color: transparent transparent;
  -ms-overflow-style: none;
  mask-image: linear-gradient(to bottom,
    transparent 0%,
    black 8%,
    black 92%,
    transparent 100%
  );
}
.toc::-webkit-scrollbar,
.toc::-webkit-scrollbar-track,
.toc::-webkit-scrollbar-thumb,
.toc::-webkit-scrollbar-corner { width: 0 !important; height: 0 !important; background: transparent !important; }
.toc-title {
  font-size: 0.76rem; font-weight: 700; color: var(--fg-sec);
  text-transform: uppercase; letter-spacing: 0.1em; margin-bottom: 0.6rem;
  font-family: var(--sans);
}
.toc .toc-item {
  display: block; line-height: 1.55; color: var(--fg-sec); text-decoration: none;
  padding: 0.15rem 0 0.15rem 0.7rem; border-left: 1.5px solid transparent;
  transition: color 0.15s, border-color 0.15s;
}
.toc .toc-item.toc-level-0 {
  font-size: 0.96rem;
  font-weight: 700;
  margin-top: 0.3rem;
  margin-bottom: 0.15rem;
  color: var(--fg);
}
.toc .toc-item.toc-level-1 {
  font-size: 0.87rem;
  font-weight: 500;
  padding-left: 1.45rem;
  color: var(--fg-muted);
  position: relative;
}
.toc .toc-item.toc-level-2 {
  font-size: 0.82rem;
  font-weight: 400;
  padding-left: 2.1rem;
  color: var(--fg-muted);
  opacity: 0.9;
  position: relative;
}
.toc .toc-item.toc-level-1::before,
.toc .toc-item.toc-level-2::before {
  content: "";
  position: absolute;
  top: 0.28rem;
  bottom: 0.28rem;
  width: 1px;
  background: var(--border);
}
.toc .toc-item.toc-level-1::before { left: 1rem; }
.toc .toc-item.toc-level-2::before { left: 1.65rem; }
.toc .toc-item.toc-level-0 { border-left-color: transparent; }
.toc .toc-item:hover { color: var(--fg); }
.toc .toc-item.active { color: var(--accent-dark); border-left-color: var(--accent); font-weight: 500; }

/* ── 页脚 ── */
.site-footer {
  text-align: center; padding: 2.5rem 1rem; font-size: 0.85rem;
  color: var(--fg-muted); border-top: 1px solid var(--border);
}
.site-footer a { color: var(--accent-dark); text-decoration: none; }
.site-footer a:hover { text-decoration: underline; }

/* ══════════════════════════════════════════════
   响应式
   ══════════════════════════════════════════════ */
@media (max-width: 1100px) {
  .toc { display: none; }
}
@media (max-width: 900px) {
  .sidebar-timeline, .sidebar-cats { display: none; }
  .home-body { padding: 0 1.2rem 3rem; }
  .post-entries { max-width: 100%; }
}
@media (max-width: 600px) {
  .hero-title { font-size: 2.8rem; }
  .hero-subtitle { font-size: 1.05rem; }
  .hero { min-height: 70vh; }
  .layout { padding: 2.5rem 1.2rem 2rem; }
  .post-header h1 { font-size: 1.8rem; }
}