:root {
  --bg: #f4f0e8;
  --surface: #fffdf8;
  --surface-strong: #f8f5ef;
  --text: #161616;
  --muted: #5a5f52;
  --line: #d9d1c5;
  --accent: #0e8a6d;
  --accent-soft: #d8efe8;
  --shadow: 0 18px 50px rgba(34, 36, 31, 0.08);
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  font-family: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", serif;
  color: var(--text);
  background:
    linear-gradient(180deg, rgba(14, 138, 109, 0.08), transparent 28%),
    linear-gradient(135deg, #f7f2e8 0%, #efe7da 100%);
}

body {
  line-height: 1.6;
}

a {
  color: inherit;
}

code {
  padding: 0.1rem 0.35rem;
  border-radius: 6px;
  background: rgba(14, 138, 109, 0.08);
  font-family: "SFMono-Regular", Consolas, monospace;
  font-size: 0.92em;
}

pre {
  overflow-x: auto;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #f6f3ec;
}

.shell {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  padding: 1.5rem 1.2rem;
  border-right: 1px solid rgba(0, 0, 0, 0.08);
  background: rgba(255, 253, 248, 0.86);
  backdrop-filter: blur(12px);
}

.sidebar__header {
  margin-bottom: 1.5rem;
}

.sidebar__header h1 {
  margin: 0;
  font-size: 1.9rem;
  line-height: 1.05;
}

.sidebar__text {
  margin: 0.65rem 0 0;
  color: var(--muted);
}

.eyebrow {
  margin: 0 0 0.4rem;
  color: var(--accent);
  font-family: "Avenir Next", "Helvetica Neue", sans-serif;
  font-size: 0.78rem;
  text-transform: uppercase;
}

.tree {
  font-family: "Avenir Next", "Helvetica Neue", sans-serif;
  font-size: 0.96rem;
}

.tree__group {
  margin: 0;
  padding-left: 0.9rem;
  list-style: none;
  border-left: 1px solid rgba(14, 138, 109, 0.16);
}

.tree__item + .tree__item {
  margin-top: 0.28rem;
}

.tree__link {
  display: inline-block;
  padding: 0.22rem 0.35rem;
  border-radius: 6px;
  text-decoration: none;
  color: var(--muted);
}

.tree__link:hover,
.tree__link--active {
  color: var(--text);
  background: var(--accent-soft);
}

.content {
  padding: 2rem;
}

.hero {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: end;
  margin-bottom: 1.4rem;
}

.hero h2 {
  margin: 0;
  font-size: clamp(2rem, 4vw, 3.6rem);
  line-height: 0.98;
}

.hero__meta {
  max-width: 30rem;
  margin: 0;
  color: var(--muted);
  font-family: "Avenir Next", "Helvetica Neue", sans-serif;
}

.overview {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.9rem;
  margin-bottom: 1.2rem;
}

.overview__panel,
.article,
.empty-state {
  border: 1px solid rgba(0, 0, 0, 0.08);
  border-radius: 8px;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.overview__panel {
  padding: 1rem 1.1rem;
}

.overview__label {
  margin: 0 0 0.35rem;
  color: var(--muted);
  font-family: "Avenir Next", "Helvetica Neue", sans-serif;
  font-size: 0.82rem;
  text-transform: uppercase;
}

.overview__text {
  margin: 0;
}

.breadcrumbs,
.chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: center;
}

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

.chip {
  display: inline-flex;
  align-items: center;
  padding: 0.22rem 0.56rem;
  border-radius: 999px;
  background: var(--surface-strong);
  border: 1px solid var(--line);
  text-decoration: none;
}

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

.article,
.empty-state {
  padding: 1.5rem 1.8rem;
}

.article h1,
.article h2,
.article h3 {
  line-height: 1.14;
}

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

.math-inline {
  display: inline-block;
  max-width: 100%;
}

.math-block {
  overflow-x: auto;
  margin: 1.2rem 0;
  padding: 0.9rem 1rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #f6f3ec;
}

.math-block mjx-container {
  margin: 0 !important;
}

@media (max-width: 900px) {
  .shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    border-right: 0;
    border-bottom: 1px solid rgba(0, 0, 0, 0.08);
  }

  .content {
    padding: 1.2rem;
  }

  .hero {
    flex-direction: column;
    align-items: start;
  }

  .overview {
    grid-template-columns: 1fr;
  }
}