:root {
  --bg: #f6f4ef;
  --surface: #fdfcfa;
  --text: #2c2a26;
  --muted: #5c574f;
  --accent: #4a6f5e;
  --accent-soft: #e3ebe6;
  --border: #e2ddd4;
  --shadow: 0 1px 2px rgba(44, 42, 38, 0.06);
  --radius: 12px;
  --font: "Segoe UI", system-ui, -apple-system, sans-serif;
  --max: 72rem;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font);
  font-size: 1.05rem;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
}

.wrap {
  max-width: var(--max);
  margin-inline: auto;
  padding-inline: clamp(1rem, 4vw, 2rem);
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--accent);
  color: #fff;
  padding: 0.5rem 1rem;
  z-index: 100;
}

.skip-link:focus {
  left: 1rem;
  top: 1rem;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.site-header {
  padding: clamp(2rem, 5vw, 3.25rem) 0 1.5rem;
  border-bottom: 1px solid var(--border);
  background: linear-gradient(180deg, #faf8f3 0%, var(--bg) 100%);
}

.site-title {
  margin: 0 0 0.5rem;
  font-size: clamp(1.55rem, 3vw, 2rem);
  font-weight: 600;
  letter-spacing: -0.02em;
}

.site-lead {
  margin: 0 0 1.25rem;
  max-width: 52ch;
  color: var(--muted);
  font-size: 1rem;
}

.search input {
  width: min(100%, 22rem);
  padding: 0.65rem 0.85rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--surface);
  font: inherit;
  box-shadow: var(--shadow);
}

.search input:focus {
  outline: 2px solid var(--accent-soft);
  outline-offset: 2px;
  border-color: #c5d4cb;
}

.layout {
  display: grid;
  gap: 2rem;
  padding-block: 2rem 3rem;
}

@media (min-width: 900px) {
  .layout {
    grid-template-columns: 14rem 1fr;
    align-items: start;
    gap: 3rem;
  }

  .toc {
    position: sticky;
    top: 1.25rem;
  }
}

.toc-label {
  margin: 0 0 0.6rem;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}

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

.toc-list li {
  margin-bottom: 0.35rem;
}

.toc-list a {
  color: var(--muted);
  text-decoration: none;
  padding: 0.25rem 0;
  display: inline-block;
  border-radius: 4px;
}

.toc-list a:hover,
.toc-list a:focus-visible {
  color: var(--accent);
}

.main {
  min-width: 0;
}

.chapter {
  margin-bottom: 2.75rem;
}

.chapter-title {
  margin: 0 0 1rem;
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--accent);
  padding-bottom: 0.35rem;
  border-bottom: 1px solid var(--accent-soft);
}

.terms {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.card {
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--surface);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.term-toggle {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem 1.1rem;
  border: 0;
  background: transparent;
  cursor: pointer;
  font: inherit;
  text-align: left;
  color: inherit;
}

.term-toggle:hover {
  background: #faf9f6;
}

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

.term-name {
  font-weight: 500;
}

.chevron {
  flex-shrink: 0;
  width: 0.55rem;
  height: 0.55rem;
  border-right: 2px solid var(--muted);
  border-bottom: 2px solid var(--muted);
  transform: rotate(45deg);
  transition: transform 0.2s ease;
}

.term-toggle[aria-expanded="true"] .chevron {
  transform: rotate(-135deg);
}

.term-panel {
  padding: 0 1.1rem 1.1rem;
  border-top: 1px solid var(--border);
}

.term-desc {
  margin: 0.85rem 0 0;
  color: var(--muted);
  max-width: 65ch;
}

.empty-msg {
  color: var(--muted);
  padding: 2rem 0;
}

.site-footer {
  padding: 2rem 0 3rem;
  color: var(--muted);
  font-size: 0.9rem;
  border-top: 1px solid var(--border);
}

.site-footer p {
  margin: 0;
}