:root {
  --bg: #ffffff;
  --surface: #ffffff;
  --text: #111111;
  --text-2: #6e6e6e;
  --border: #e5e5e5;
  --border-strong: #cfcfcf;
  --accent: #002fa7;
  --accent-soft: #eef2fc;
  --hover: #f7f7f7;
}

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

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.75;
  font-size: 16px;
}

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

.container {
  max-width: 760px;
  margin: 0 auto;
  padding: 0 24px;
}

.site-header {
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.brand {
  display: inline-flex;
  align-items: center;
  font-size: 18px;
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
  letter-spacing: 0.02em;
}

.brand::before {
  content: "";
  width: 10px;
  height: 10px;
  background: var(--accent);
  margin-right: 10px;
  flex: none;
}

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

.nav-links a {
  margin-left: 24px;
  color: var(--text-2);
  text-decoration: none;
  font-size: 15px;
}

.nav-links a:hover {
  color: var(--text);
}

.nav-links a.active {
  color: var(--accent);
  font-weight: 600;
}

main {
  padding: 64px 24px 96px;
}

.kicker {
  font-family: "SF Mono", Consolas, "JetBrains Mono", Menlo, monospace;
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 18px;
}

.hero {
  margin-bottom: 64px;
}

.hero h1 {
  font-size: 40px;
  line-height: 1.25;
  letter-spacing: -0.02em;
  margin-bottom: 16px;
}

.hero .lead {
  color: var(--text-2);
  font-size: 17px;
  margin-bottom: 32px;
  max-width: 560px;
}

.search-box input {
  width: 100%;
  max-width: 480px;
  height: 48px;
  padding: 0 16px;
  font-size: 15px;
  font-family: inherit;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border-strong);
  border-radius: 6px;
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.search-box input::placeholder {
  color: #9a9a9a;
}

.search-box input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 4px;
}

.section-head h2 {
  font-size: 15px;
  font-weight: 600;
  letter-spacing: 0.08em;
}

.more-link {
  color: var(--accent);
  text-decoration: none;
  font-size: 14px;
}

.more-link:hover {
  text-decoration: underline;
}

/* 笔记列表：编号行式极简布局 */
.note-row {
  display: grid;
  grid-template-columns: 72px 1fr;
  gap: 8px;
  padding: 20px 0;
  border-bottom: 1px solid var(--border);
}

.note-id {
  font-family: "SF Mono", Consolas, "JetBrains Mono", Menlo, monospace;
  font-size: 13px;
  color: var(--text-2);
  padding-top: 3px;
  transition: color 0.12s;
}

.note-row:hover .note-id {
  color: var(--accent);
}

.note-title {
  font-size: 17px;
  font-weight: 600;
  line-height: 1.5;
  margin-bottom: 4px;
}

.note-title a {
  color: var(--text);
  text-decoration: none;
  transition: color 0.12s;
}

.note-title a:hover {
  color: var(--accent);
}

.note-meta {
  font-family: "SF Mono", Consolas, "JetBrains Mono", Menlo, monospace;
  font-size: 12.5px;
  color: var(--text-2);
  margin-bottom: 6px;
}

.note-excerpt {
  font-size: 14.5px;
  color: var(--text-2);
  margin-bottom: 10px;
}

.note-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.tag {
  display: inline-block;
  padding: 2px 10px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: transparent;
  font-family: inherit;
  font-size: 12.5px;
  line-height: 1.5;
  color: var(--text-2);
  user-select: none;
  transition: color 0.12s, border-color 0.12s, background 0.12s;
}

span.tag {
  cursor: default;
}

span.tag:hover {
  border-color: var(--border);
  color: var(--text-2);
}

button.tag {
  cursor: pointer;
}

button.tag:hover {
  border-color: var(--accent);
  color: var(--accent);
}

button.tag.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.tag-bar {
  margin-top: 20px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.empty {
  color: var(--text-2);
  text-align: center;
  padding: 48px 0;
  border: 1px dashed var(--border);
  border-radius: 6px;
  margin-top: 16px;
}

/* 文章与关于页 */
.page {
  padding-top: 8px;
}

.page h1 {
  font-size: 32px;
  letter-spacing: -0.015em;
  line-height: 1.3;
  margin-bottom: 14px;
}

.page .meta {
  font-family: "SF Mono", Consolas, "JetBrains Mono", Menlo, monospace;
  font-size: 12.5px;
  color: var(--text-2);
  margin-bottom: 12px;
}

.page h2 {
  font-size: 19px;
  font-weight: 600;
  margin: 40px 0 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
}

.page p,
.page ul,
.page ol {
  margin-bottom: 16px;
}

.page ul,
.page ol {
  padding-left: 24px;
}

.page a {
  color: var(--accent);
}

.page code {
  background: var(--hover);
  border: 1px solid var(--border);
  padding: 1px 6px;
  border-radius: 4px;
  font-size: 0.9em;
  font-family: Consolas, "SF Mono", monospace;
}

/* 三线表（学术规范：仅顶线、栏目线、底线，无竖线） */
.page table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 16px;
  font-size: 14px;
  border-top: 2px solid var(--text);
  border-bottom: 2px solid var(--text);
}

.page thead th {
  border-bottom: 1px solid var(--text);
  padding: 8px 10px;
  text-align: left;
  font-weight: 600;
}

.page tbody td {
  border: none;
  padding: 8px 10px;
  text-align: left;
}

.back-link {
  margin-top: 48px;
}

.back-link a {
  color: var(--accent);
  text-decoration: none;
}

.back-link a:hover {
  text-decoration: underline;
}

.note-box {
  border-left: 3px solid var(--accent);
  background: var(--accent-soft);
  padding: 14px 18px;
  margin: 24px 0;
  font-size: 14.5px;
  color: var(--text);
  border-radius: 0 6px 6px 0;
}

.site-footer {
  border-top: 1px solid var(--border);
  padding: 28px 0;
  color: var(--text-2);
  font-size: 13px;
  text-align: center;
}

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

@media (prefers-reduced-motion: reduce) {
  * {
    transition: none !important;
  }
}

@media (max-width: 480px) {
  main {
    padding: 48px 20px 72px;
  }

  .hero h1 {
    font-size: 30px;
  }

  .nav-links a {
    margin-left: 16px;
  }

  .note-row {
    grid-template-columns: 56px 1fr;
  }
}

/* ---------- 文章目录 ---------- */
.toc {
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 16px 20px;
  margin: 24px 0 8px;
  background: var(--surface);
}

.toc-title {
  font-family: "SF Mono", Consolas, "JetBrains Mono", Menlo, monospace;
  font-size: 12px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
}

.toc ol {
  list-style: none;
  padding: 0;
  margin: 0;
}

.toc li {
  border-bottom: 1px solid var(--border);
}

.toc li:last-child {
  border-bottom: none;
}

.toc a {
  display: block;
  padding: 7px 0;
  color: var(--text-2);
  text-decoration: none;
  font-size: 14px;
  transition: color 0.12s, padding-left 0.12s;
}

.toc a:hover {
  color: var(--accent);
  padding-left: 4px;
}

/* ---------- 上一篇 / 下一篇 ---------- */
.post-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 40px 0 8px;
  border-top: 1px solid var(--border);
  padding-top: 20px;
}

.post-nav-link {
  display: block;
  color: var(--text);
  text-decoration: none;
  font-size: 15px;
  font-weight: 600;
  transition: color 0.12s;
}

.post-nav-link:hover {
  color: var(--accent);
}

.post-nav-link span {
  display: block;
  font-family: "SF Mono", Consolas, "JetBrains Mono", Menlo, monospace;
  font-size: 12px;
  font-weight: 400;
  letter-spacing: 0.12em;
  color: var(--text-2);
  margin-bottom: 4px;
}

.post-nav-link:last-child {
  text-align: right;
}

/* ---------- 相关笔记 ---------- */
.related {
  margin: 40px 0 8px;
}

.related h2 {
  margin: 0 0 12px;
}

.related-item {
  display: flex;
  flex-direction: column;
  padding: 14px 0;
  border-bottom: 1px solid var(--border);
  text-decoration: none;
}

.related-title {
  color: var(--text);
  font-size: 15px;
  font-weight: 600;
  transition: color 0.12s;
}

.related-item:hover .related-title {
  color: var(--accent);
}

.related-meta {
  font-family: "SF Mono", Consolas, "JetBrains Mono", Menlo, monospace;
  font-size: 12px;
  color: var(--text-2);
  margin-top: 2px;
}

@media (max-width: 480px) {
  .post-nav {
    grid-template-columns: 1fr;
  }

  .post-nav-link:last-child {
    text-align: left;
  }
}