:root {
  --bg: #f6efe4;
  --bg-accent: #efe2cc;
  --panel: rgba(255, 250, 242, 0.84);
  --panel-strong: #fffdf9;
  --text: #1d2430;
  --muted: #596575;
  --line: rgba(39, 51, 64, 0.12);
  --primary: #b5512d;
  --primary-deep: #8d3d22;
  --secondary: #204b57;
  --shadow: 0 20px 45px rgba(38, 35, 28, 0.12);
  --radius: 24px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", "Aptos", "Trebuchet MS", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at top left, rgba(181, 81, 45, 0.14), transparent 26%),
    radial-gradient(circle at bottom right, rgba(32, 75, 87, 0.18), transparent 30%),
    linear-gradient(180deg, var(--bg), #f8f4ed 56%, #f0e3cf);
}

button {
  font: inherit;
  cursor: pointer;
  border: none;
}

.page-shell {
  width: min(1200px, calc(100vw - 32px));
  margin: 0 auto;
  padding: 32px 0 48px;
}

.hero {
  padding: 32px;
  margin-bottom: 24px;
  border-radius: calc(var(--radius) + 8px);
  background:
    linear-gradient(135deg, rgba(255, 253, 249, 0.95), rgba(255, 245, 232, 0.86)),
    var(--panel);
  border: 1px solid rgba(181, 81, 45, 0.12);
  box-shadow: var(--shadow);
}

.eyebrow,
.card-kicker,
.stat-label,
.hint,
.badge {
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.73rem;
}

.eyebrow,
.card-kicker,
.badge {
  color: var(--primary);
  font-weight: 700;
}

.hero h1,
.panel h2,
.flashcard h2 {
  font-family: "Book Antiqua", "Palatino Linotype", "Georgia", serif;
  line-height: 1.05;
  margin: 0;
}

.hero h1 {
  font-size: clamp(2.4rem, 5vw, 4.6rem);
  max-width: 12ch;
}

.hero-copy {
  max-width: 58ch;
  color: var(--muted);
  font-size: 1.02rem;
  line-height: 1.7;
  margin: 18px 0 0;
}

.hero-actions,
.nav-buttons {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 24px;
}

.grid {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  gap: 24px;
  align-items: start;
}

.panel {
  border-radius: var(--radius);
  background: var(--panel);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  backdrop-filter: blur(16px);
}

.control-panel,
.list-panel {
  padding: 24px;
}

.card-panel {
  padding: 20px;
  min-height: 610px;
}

.list-panel {
  grid-column: 1 / -1;
}

.panel-head p,
.hint,
.stat-label {
  color: var(--muted);
}

.panel-head h2 {
  font-size: 1.6rem;
}

.panel-head p {
  margin: 10px 0 0;
  line-height: 1.6;
}

.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 22px 0;
}

.filter-btn,
.secondary-btn,
.primary-btn,
.ghost-btn {
  border-radius: 999px;
  padding: 12px 16px;
  transition: transform 120ms ease, background 160ms ease, color 160ms ease;
}

.filter-btn {
  background: rgba(32, 75, 87, 0.08);
  color: var(--secondary);
}

.filter-btn.active {
  background: var(--secondary);
  color: #fff;
}

.primary-btn {
  background: var(--primary);
  color: #fff;
}

.primary-btn:hover,
.secondary-btn:hover,
.ghost-btn:hover,
.filter-btn:hover {
  transform: translateY(-1px);
}

.secondary-btn {
  background: rgba(32, 75, 87, 0.12);
  color: var(--secondary);
}

.ghost-btn {
  background: transparent;
  color: var(--primary);
  border: 1px solid rgba(181, 81, 45, 0.24);
}

.stats {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  padding: 18px;
  background: var(--panel-strong);
  border-radius: 20px;
  border: 1px solid var(--line);
}

.stats strong {
  display: block;
  margin-top: 3px;
  font-size: 1.35rem;
}

.card-topline {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: center;
  margin-bottom: 16px;
}

.flashcard {
  position: relative;
  min-height: 520px;
  border-radius: 28px;
  overflow: hidden;
  border: 1px solid rgba(32, 75, 87, 0.12);
  background:
    linear-gradient(140deg, rgba(255, 250, 245, 0.98), rgba(243, 234, 217, 0.92));
  outline: none;
}

.card-face {
  position: absolute;
  inset: 0;
  padding: 28px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  transition: opacity 180ms ease;
}

.card-front {
  background:
    radial-gradient(circle at top right, rgba(181, 81, 45, 0.12), transparent 28%),
    linear-gradient(160deg, rgba(255, 255, 255, 0.85), rgba(246, 237, 225, 0.9));
}

.card-back {
  opacity: 0;
  pointer-events: none;
  background:
    radial-gradient(circle at bottom left, rgba(32, 75, 87, 0.14), transparent 30%),
    linear-gradient(160deg, rgba(255, 255, 255, 0.95), rgba(236, 246, 245, 0.9));
}

.flashcard.is-flipped .card-front {
  opacity: 0;
  pointer-events: none;
}

.flashcard.is-flipped .card-back {
  opacity: 1;
  pointer-events: auto;
}

.flashcard h2 {
  margin-top: 8px;
  font-size: clamp(1.8rem, 3.7vw, 3.2rem);
  max-width: 16ch;
}

.card-answer {
  font-size: 1.02rem;
  line-height: 1.8;
  color: var(--text);
  max-width: 58ch;
}

.card-answer p {
  margin: 0 0 12px;
}

.card-answer p:last-child {
  margin-bottom: 0;
}

.card-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 14px;
  margin-top: 22px;
}

.list-card {
  text-align: left;
  padding: 16px;
  border-radius: 18px;
  background: rgba(255, 255, 255, 0.75);
  border: 1px solid var(--line);
  min-height: 124px;
}

.list-card.active {
  border-color: rgba(181, 81, 45, 0.4);
  box-shadow: inset 0 0 0 1px rgba(181, 81, 45, 0.18);
}

.list-card span {
  display: block;
  color: var(--primary);
  font-size: 0.77rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 10px;
}

.list-card strong {
  display: block;
  font-size: 1rem;
  line-height: 1.5;
  color: var(--text);
}

@media (max-width: 960px) {
  .grid {
    grid-template-columns: 1fr;
  }

  .card-panel,
  .list-panel {
    grid-column: auto;
  }

  .flashcard {
    min-height: 460px;
  }
}

@media (max-width: 640px) {
  .page-shell {
    width: min(100vw - 18px, 100%);
    padding-top: 12px;
  }

  .hero,
  .control-panel,
  .card-panel,
  .list-panel {
    padding: 18px;
  }

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

  .flashcard {
    min-height: 420px;
  }

  .card-face {
    padding: 22px;
  }
}