:root {
  color-scheme: light;
  --paper: #fbfaf7;
  --ink: #25211b;
  --muted: #70695f;
  --line: #ded7ca;
  --accent: #8c4b32;
  --accent-soft: #f1dfd6;
  --green: #2f6f4e;
  --red: #9b3f33;
  --card: #fffdf9;
  --tile: #ffffff;
  --quote-ink: #463b32;
  --choice: #ffffff;
  --correct-soft: #e8f3ed;
  --wrong-soft: #f7e5e1;
  --shadow: 0 18px 45px rgba(42, 31, 20, 0.08);
  font-family: ui-serif, Georgia, Cambria, "Times New Roman", serif;
}

:root.dark {
  color-scheme: dark;
  --paper: #171615;
  --ink: #f0e9dd;
  --muted: #b9ad9e;
  --line: #3e3730;
  --accent: #e0a37f;
  --accent-soft: rgba(140, 75, 50, 0.23);
  --green: #8fd0ad;
  --red: #eba091;
  --card: #211f1c;
  --tile: #24211e;
  --quote-ink: #e3d8ca;
  --choice: #24211e;
  --correct-soft: rgba(47, 111, 78, 0.22);
  --wrong-soft: rgba(155, 63, 51, 0.22);
  --shadow: 0 18px 45px rgba(0, 0, 0, 0.28);
}

@media (prefers-color-scheme: dark) {
  :root:not(.light) {
    color-scheme: dark;
    --paper: #171615;
    --ink: #f0e9dd;
    --muted: #b9ad9e;
    --line: #3e3730;
    --accent: #e0a37f;
    --accent-soft: rgba(140, 75, 50, 0.23);
    --green: #8fd0ad;
    --red: #eba091;
    --card: #211f1c;
    --tile: #24211e;
    --quote-ink: #e3d8ca;
    --choice: #24211e;
    --correct-soft: rgba(47, 111, 78, 0.22);
    --wrong-soft: rgba(155, 63, 51, 0.22);
    --shadow: 0 18px 45px rgba(0, 0, 0, 0.28);
  }
}

* { box-sizing: border-box; }
html {
  background: var(--paper);
  color: var(--ink);
  scrollbar-color: var(--line) var(--paper);
}
body { margin: 0; line-height: 1.58; }
::-webkit-scrollbar { width: 12px; height: 12px; }
::-webkit-scrollbar-track { background: var(--paper); }
::-webkit-scrollbar-thumb { background: var(--line); border: 3px solid var(--paper); border-radius: 999px; }
::-webkit-scrollbar-thumb:hover { background: var(--accent); }
main, header { max-width: 860px; margin: 0 auto; padding: 0 24px; }
header { padding-top: 56px; padding-bottom: 24px; }
main { padding-bottom: 48px; }

h1, h2, h3 { line-height: 1.12; margin: 0; overflow-wrap: break-word; hyphens: auto; }
h1 { font-size: clamp(2.05rem, 6vw, 4.4rem); font-weight: 650; letter-spacing: -0.04em; }
h2 { font-size: clamp(1.45rem, 3vw, 2.1rem); margin-top: 46px; border-top: 1px solid var(--line); padding-top: 28px; }
h3 { font-size: 1.15rem; margin-top: 26px; }
p { margin: 0.85rem 0; }
a { color: var(--accent); text-underline-offset: 0.18em; }
small, .muted { color: var(--muted); }

.card, .quiz-card, .practice {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 22px;
  box-shadow: var(--shadow);
  padding: 22px;
  margin: 22px 0;
}
.grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; margin: 22px 0; }
.tile {
  border: 1px solid var(--line);
  background: var(--tile);
  border-radius: 18px;
  padding: 16px;
}
.tile strong { display: block; color: var(--accent); margin-bottom: 6px; }

ol, ul { padding-left: 1.25rem; }
li + li { margin-top: 0.45rem; }
blockquote {
  margin: 24px 0;
  border-left: 4px solid var(--accent);
  padding: 8px 0 8px 18px;
  color: var(--quote-ink);
  background: linear-gradient(90deg, var(--accent-soft), transparent 76%);
}

.quiz-options { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 14px; }
button.choice {
  appearance: none;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--choice);
  color: var(--ink);
  min-height: 44px;
  padding: 10px 14px;
  cursor: pointer;
  font: 700 0.92rem/1 ui-sans-serif, system-ui, sans-serif;
}
button.choice:hover { border-color: var(--accent); }
button.choice.correct { border-color: var(--green); background: var(--correct-soft); }
button.choice.wrong { border-color: var(--red); background: var(--wrong-soft); }
.feedback { margin-top: 14px; font-weight: 650; }
.feedback.correct { color: var(--green); }
.feedback.wrong { color: var(--red); }

.sources {
  font-size: 0.92rem;
  color: var(--muted);
  border-top: 1px solid var(--line);
  margin-top: 34px;
  padding-top: 18px;
}

.lesson-progress {
  display: inline-flex;
  margin-top: 10px;
  padding: 5px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  background: var(--card);
  font: 700 0.82rem/1.2 ui-sans-serif, system-ui, sans-serif;
}

.lesson-nav {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 10px;
  align-items: stretch;
  border-top: 1px solid var(--line);
  margin-top: 34px;
  padding-top: 18px;
}

.lesson-nav__item {
  display: flex;
  align-items: center;
  min-height: 48px;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--card);
  padding: 10px 14px;
  text-decoration: none;
  color: var(--accent);
  font: 700 0.92rem/1.35 ui-sans-serif, system-ui, sans-serif;
}
.lesson-nav__item:hover { border-color: var(--accent); }
.lesson-nav__item--center { justify-content: center; white-space: nowrap; }
.lesson-nav__item--disabled { color: var(--muted); background: transparent; }

@media (max-width: 720px) {
  main, header { padding-left: 18px; padding-right: 18px; }
  header { padding-top: 34px; }
  h1 { font-size: clamp(1.9rem, 8vw, 2.75rem); }
  .card, .quiz-card, .practice { border-radius: 20px; padding: 18px; }
  .grid, .lesson-nav { grid-template-columns: 1fr; }
  .lesson-nav__item--center { justify-content: flex-start; }
}

@media print {
  :root { --paper: white; --card: white; }
  body { font-size: 11.5pt; }
  header { padding-top: 0; }
  main, header { max-width: none; padding-left: 0; padding-right: 0; }
  .card, .quiz-card, .practice, .tile { box-shadow: none; break-inside: avoid; }
  button.choice { display: none; }
  a { color: inherit; }
}