:root {
  --bg: #f6f7fb;
  --panel: #ffffff;
  --text: #1f2937;
  --muted: #667085;
  --line: #d8dee8;
  --line-strong: #b8c2d0;
  --primary: #1d4ed8;
  --primary-soft: #e8f0ff;
  --code-bg: #f3f5f8;
  --shadow: 0 8px 24px rgba(15, 23, 42, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  font-size: 15px;
  line-height: 1.65;
}

.topbar {
  background: var(--panel);
  border-bottom: 1px solid var(--line);
  padding: 22px 28px 20px;
}

.topbar h1 {
  font-size: 26px;
  margin: 6px 0;
}

.topbar p {
  color: var(--muted);
  margin: 0;
}

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

.layout {
  display: grid;
  gap: 20px;
  grid-template-columns: minmax(260px, 330px) minmax(0, 1fr);
  max-width: 1440px;
  margin: 0 auto;
  padding: 22px 28px 40px;
}

.sidebar,
.viewer {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 12px;
  box-shadow: var(--shadow);
}

.sidebar {
  align-self: start;
  max-height: calc(100vh - 130px);
  overflow: auto;
  position: sticky;
  top: 18px;
}

.sidebar-header {
  align-items: center;
  border-bottom: 1px solid var(--line);
  display: flex;
  font-weight: 700;
  justify-content: space-between;
  padding: 14px 16px;
}

.sidebar button {
  background: var(--panel);
  border: 1px solid var(--line-strong);
  border-radius: 6px;
  color: var(--text);
  cursor: pointer;
  font: inherit;
  font-size: 13px;
  padding: 4px 9px;
}

.tree {
  padding: 12px 10px 16px;
}

.tree ul {
  list-style: none;
  margin: 0;
  padding-left: 15px;
}

.tree > ul {
  padding-left: 0;
}

.tree li {
  margin: 3px 0;
}

.tree-folder {
  color: #344054;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.02em;
  margin: 10px 0 4px;
  text-transform: none;
}

.tree a {
  border-radius: 6px;
  color: var(--text);
  display: block;
  padding: 5px 8px;
  text-decoration: none;
}

.tree a:hover,
.tree a.active {
  background: var(--primary-soft);
  color: var(--primary);
}

.viewer {
  min-height: calc(100vh - 130px);
  overflow: hidden;
}

.article-meta {
  border-bottom: 1px solid var(--line);
  color: var(--muted);
  font-size: 13px;
  padding: 12px 24px;
}

.article-content {
  max-width: 900px;
  padding: 28px 34px 52px;
}

.article-content h1 {
  font-size: 30px;
  line-height: 1.3;
  margin: 0 0 24px;
}

.article-content h2 {
  border-top: 1px solid var(--line);
  font-size: 23px;
  line-height: 1.35;
  margin: 36px 0 14px;
  padding-top: 24px;
}

.article-content h3 {
  font-size: 19px;
  margin: 28px 0 10px;
}

.article-content p {
  margin: 12px 0;
}

.article-content table {
  border-collapse: collapse;
  display: block;
  margin: 18px 0;
  overflow-x: auto;
  width: 100%;
}

.article-content th,
.article-content td {
  border: 1px solid var(--line);
  padding: 8px 10px;
  text-align: left;
  vertical-align: top;
}

.article-content th {
  background: #f5f7fa;
  font-weight: 700;
}

.article-content code {
  background: var(--code-bg);
  border-radius: 4px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.92em;
  padding: 0.1em 0.3em;
}

.article-content pre {
  background: #111827;
  border-radius: 10px;
  color: #e5e7eb;
  overflow-x: auto;
  padding: 16px 18px;
}

.article-content pre code {
  background: transparent;
  color: inherit;
  padding: 0;
}

.article-content img {
  border: 1px solid var(--line);
  border-radius: 10px;
  display: block;
  height: auto;
  margin: 20px 0;
  max-width: 100%;
}

.article-content .mermaid {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 10px;
  margin: 18px 0;
  overflow-x: auto;
  padding: 16px;
}

.article-content mjx-container[display="true"] {
  margin: 18px 0;
  max-width: 100%;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 4px 0;
}

.muted {
  color: var(--muted);
}

@media (max-width: 860px) {
  .layout {
    grid-template-columns: 1fr;
    padding: 16px;
  }

  .sidebar {
    max-height: none;
    position: static;
  }

  .article-content {
    padding: 22px 20px 42px;
  }
}