:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --bg: #f8fafc;
  --text: #0f172a;
  --muted: #64748b;
  --card: #ffffff;
}

body {
  font-family: 'Inter', sans-serif;
  color: var(--text);
  background: #fff;
}

html {
  scroll-behavior: smooth;
}

.hero-section {
  background: linear-gradient(180deg, #eef6ff 0%, #ffffff 100%);
}

.hero-card,
.lesson-card,
.quiz-card,
.feature-card,
.flashcard {
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.hero-card:hover,
.lesson-card:hover,
.feature-card:hover,
.quiz-card:hover {
  transform: translateY(-3px);
}

.flashcard-wrapper {
  perspective: 1000px;
}

.flashcard {
  width: 100%;
  height: 320px;
  cursor: pointer;
  position: relative;
  transform-style: preserve-3d;
}

.flashcard-inner {
  position: absolute;
  inset: 0;
  transform-style: preserve-3d;
  transition: transform 0.6s ease;
}

.flashcard-front,
.flashcard-back {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: 2rem;
  background: white;
  border-radius: 1.5rem;
  backface-visibility: hidden;
}

.flashcard-back {
  transform: rotateY(180deg);
}

.flashcard.flipped .flashcard-inner {
  transform: rotateY(180deg);
}

.quiz-summary {
  border-left: 5px solid var(--primary);
}

#quiz-options button.correct {
  background: #dcfce7;
  border-color: #22c55e;
  color: #166534;
}

#quiz-options button.wrong {
  background: #fee2e2;
  border-color: #ef4444;
  color: #991b1b;
}