:root {
  color-scheme: light;
  --aeon-bg: #F2F6F3;
  --aeon-card: #FFFFFF;
  --aeon-surface: #E8F0EB;
  --aeon-accent: #2E5A3C;
  --aeon-highlight: #3A7A52;
  --aeon-text: #1A2E24;
  --aeon-muted: #5A6F64;
  --aeon-mono: #2E6B48;
  --aeon-on-green: #E5EDE8;
  --aeon-border: rgba(46, 90, 60, 0.14);
  --aeon-border-strong: rgba(46, 90, 60, 0.22);
  --aeon-shadow-sm: 0 2px 12px rgba(46, 90, 60, 0.06);
  --aeon-shadow-md: 0 8px 28px rgba(46, 90, 60, 0.1);
  --aeon-inset: rgba(46, 90, 60, 0.05);
  --aeon-diagram-frame: rgba(46, 90, 60, 0.04);
  --header-h: 3.75rem;
  --footer-h: 2.25rem;
}

[data-theme="dark"] {
  color-scheme: dark;
  --aeon-bg: #101512;
  --aeon-card: #1A221E;
  --aeon-surface: #242E29;
  --aeon-accent: #4A9468;
  --aeon-highlight: #5CAD7E;
  --aeon-text: #E5EDE8;
  --aeon-muted: #9AADA3;
  --aeon-mono: #7BC49A;
  --aeon-on-green: #E5EDE8;
  --aeon-border: rgba(126, 184, 154, 0.14);
  --aeon-border-strong: rgba(126, 184, 154, 0.24);
  --aeon-shadow-sm: 0 2px 16px rgba(0, 0, 0, 0.28);
  --aeon-shadow-md: 0 10px 32px rgba(0, 0, 0, 0.38);
  --aeon-inset: rgba(0, 0, 0, 0.18);
  --aeon-diagram-frame: rgba(0, 0, 0, 0.22);
}

html {
  scroll-padding-top: calc(var(--header-h) + 1rem);
}

body {
  background-color: var(--aeon-bg);
  color: var(--aeon-text);
  font-family: 'EB Garamond', Georgia, serif;
  -webkit-font-smoothing: antialiased;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  padding-top: var(--header-h);
}

main {
  flex: 1 0 auto;
}

.font-display { font-family: 'Playfair Display', Georgia, serif; }
.font-mono-tech { font-family: 'DejaVu Sans Mono', Consolas, Monaco, monospace; }

.hairline-b { border-bottom: 1px solid var(--aeon-border); }

/* Tailwind utility aliases — follow CSS variables for theme support */
.text-aeon-text { color: var(--aeon-text); }
.text-aeon-muted { color: var(--aeon-muted); }
.text-aeon-mono { color: var(--aeon-mono); }
.text-aeon-on-green { color: var(--aeon-on-green); }
.bg-aeon-text\/20 { background-color: color-mix(in srgb, var(--aeon-text) 20%, transparent); }

/* ── Theme toggle ── */
.theme-toggle {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  border: 1px solid rgba(229, 237, 232, 0.45);
  border-radius: 999px;
  background: rgba(0, 0, 0, 0.22);
  color: var(--aeon-on-green);
  cursor: pointer;
  flex-shrink: 0;
  appearance: none;
  -webkit-appearance: none;
  transition: background 0.2s ease, border-color 0.2s ease, transform 0.15s ease;
  z-index: 2;
}

.theme-toggle:hover {
  background: rgba(0, 0, 0, 0.26);
  border-color: rgba(229, 237, 232, 0.55);
}

.theme-toggle:active {
  transform: scale(0.96);
}

.theme-toggle__icon {
  position: absolute;
  width: 1.1rem;
  height: 1.1rem;
  transition: opacity 0.2s ease, transform 0.2s ease;
  pointer-events: none;
}

.theme-toggle__icon svg {
  display: block;
  width: 100%;
  height: 100%;
}

.theme-toggle__icon--sun {
  opacity: 1;
  transform: scale(1) rotate(0deg);
  color: #ffe9a8;
}

.theme-toggle__icon--moon {
  opacity: 0;
  transform: scale(0.75) rotate(-18deg);
  color: #e5ede8;
}

[data-theme="dark"] .theme-toggle__icon--sun {
  opacity: 0;
  transform: scale(0.75) rotate(18deg);
}

[data-theme="dark"] .theme-toggle__icon--moon {
  opacity: 1;
  transform: scale(1) rotate(0deg);
}

.site-header nav {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  justify-content: flex-start;
  width: 100%;
  height: 100%;
}

.site-header nav > a:first-child {
  margin-right: 0;
}

.site-header__tools {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-shrink: 0;
  position: relative;
  z-index: 2;
}

/* ── Fixed green header ── */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 50;
  height: var(--header-h);
  overflow: visible;
  background: linear-gradient(180deg, #3A7A52 0%, #2E5A3C 100%);
  border-bottom: 1px solid rgba(30, 61, 40, 0.35);
  box-shadow: 0 2px 12px rgba(30, 61, 40, 0.12);
  transform: translateY(0);
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1), box-shadow 0.3s ease;
  will-change: transform;
}

.site-header.nav-scrolled {
  box-shadow: 0 4px 20px rgba(30, 61, 40, 0.2);
}

.site-header.header-hidden {
  transform: translateY(-100%);
  box-shadow: none;
}

.site-header a,
.site-header button {
  color: var(--aeon-on-green);
}

.site-header .nav-link {
  color: rgba(229, 237, 232, 0.82);
}
.site-header .nav-link:hover {
  color: var(--aeon-on-green);
}

.logo-mark {
  object-fit: contain;
  image-rendering: pixelated;
  image-rendering: crisp-edges;
}

/* ── Site footer (document flow — scroll to reach on long pages) ── */
.site-footer {
  flex-shrink: 0;
  margin-top: auto;
  height: var(--footer-h);
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(180deg, #2E5A3C 0%, #1E3D28 100%);
  border-top: 1px solid rgba(126, 184, 154, 0.15);
  color: rgba(229, 237, 232, 0.85);
}

.site-footer__inner {
  width: 100%;
  max-width: 48rem;
  margin: 0 auto;
  padding: 0 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

.site-footer__copy {
  margin: 0;
  font-size: 0.6875rem;
  line-height: 1;
  opacity: 0.85;
  text-align: center;
  letter-spacing: 0.02em;
}

.site-footer a {
  color: rgba(229, 237, 232, 0.75);
  transition: color 0.2s ease;
}
.site-footer a:hover {
  color: var(--aeon-on-green);
}

/* ── Intro ── */
.page-intro {
  max-width: 36rem;
}

/* ── Home guide hub ── */
.guide-hub {
  max-width: 42rem;
}

.guide-hub__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.guide-hub__card {
  display: block;
  text-decoration: none;
  background: var(--aeon-card);
  border: 1px solid var(--aeon-border);
  border-radius: 2px;
  padding: 1.5rem 1.75rem;
  box-shadow: var(--aeon-shadow-sm);
  transition: border-color 0.2s ease, box-shadow 0.2s ease, transform 0.2s ease;
}

.guide-hub__card:hover {
  border-color: var(--aeon-border-strong);
  box-shadow: var(--aeon-shadow-md);
  transform: translateY(-1px);
}

.guide-hub__title {
  display: block;
  font-size: 1.35rem;
  color: var(--aeon-text);
  margin-bottom: 0.5rem;
}

.guide-hub__desc {
  display: block;
  font-size: 1.05rem;
  line-height: 1.6;
  color: var(--aeon-muted);
  margin-bottom: 1rem;
}

.guide-hub__action {
  display: block;
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--aeon-mono);
}

.guide-hub__card:hover .guide-hub__action {
  color: var(--aeon-accent);
}

.guide-hub__tag {
  display: inline-block;
  font-family: 'DejaVu Sans Mono', Consolas, Monaco, monospace;
  font-size: 0.65rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--aeon-mono);
  margin-bottom: 0.35rem;
}

.hub-section {
  margin-bottom: 2.5rem;
}

.hub-section:last-child {
  margin-bottom: 0;
}

/* ── Curriculum table of contents ── */
.curriculum {
  max-width: 42rem;
}

.topic-block {
  border-bottom: 1px solid var(--aeon-border);
  scroll-margin-top: calc(var(--header-h) + 1.5rem);
}

.topic-block:last-child {
  border-bottom: none;
}

.topic-summary {
  display: flex;
  align-items: baseline;
  gap: 1rem;
  padding: 1.1rem 0;
  cursor: pointer;
  list-style: none;
  user-select: none;
}

.topic-summary::-webkit-details-marker {
  display: none;
}

.topic-num {
  flex-shrink: 0;
  font-size: 0.7rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--aeon-mono);
  min-width: 5.5rem;
}

.topic-title {
  flex: 1;
  font-size: 1.15rem;
  color: var(--aeon-text);
  line-height: 1.35;
}

.topic-chevron {
  flex-shrink: 0;
  width: 0.5rem;
  height: 0.5rem;
  border-right: 1.5px solid var(--aeon-muted);
  border-bottom: 1.5px solid var(--aeon-muted);
  transform: rotate(45deg);
  margin-top: 0.15rem;
  transition: transform 0.25s ease;
  opacity: 0.5;
}

.topic-block[open] .topic-chevron {
  transform: rotate(-135deg);
  margin-top: 0.35rem;
}

.topic-block[open] .topic-title {
  color: var(--aeon-accent);
}

.lesson-list {
  list-style: none;
  margin: 0 0 1rem 0;
  padding: 0 0 0.5rem 5.5rem;
}

.lesson-item {
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
  padding: 0.35rem 0;
  font-size: 1.05rem;
  color: var(--aeon-muted);
}

.lesson-num {
  flex-shrink: 0;
  font-size: 0.8rem;
  color: var(--aeon-mono);
  opacity: 0.7;
  min-width: 1.25rem;
}

.lesson-status {
  font-size: 0.72rem;
  letter-spacing: 0.04em;
  color: var(--aeon-mono);
  opacity: 0.55;
}

.lesson-list-link {
  color: var(--aeon-text);
  text-decoration: none;
  transition: color 0.2s ease;
}

.lesson-list-link:hover {
  color: var(--aeon-accent);
}

.lesson-item--available {
  color: var(--aeon-text);
}

/* ── Mobile menu ── */
#mobile-menu {
  transform: translateX(100%);
  transition: transform 0.4s cubic-bezier(0.4, 0, 0.2, 1);
  top: var(--header-h);
  bottom: 0;
  background: var(--aeon-card);
  border-left: 1px solid var(--aeon-border);
}
#mobile-menu.open { transform: translateX(0); }

::selection {
  background: rgba(58, 122, 82, 0.25);
  color: var(--aeon-text);
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}

@media (max-width: 640px) {
  :root {
    --header-h: 3.25rem;
    --footer-h: 2rem;
  }

  .site-header nav {
    gap: 0.5rem;
    padding-left: 0.875rem;
    padding-right: 0.875rem;
  }

  .site-header__tools {
    gap: 0.5rem;
  }

  .theme-toggle {
    width: 2.25rem;
    height: 2.25rem;
  }

  .site-footer__inner {
    padding: 0 0.875rem;
  }

  .site-footer__copy {
    font-size: 0.625rem;
  }

  .lesson-list {
    padding-left: 0;
  }

  .topic-summary {
    flex-wrap: wrap;
    gap: 0.25rem 1rem;
  }

  .topic-num {
    min-width: auto;
  }
}