* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  font-family:
    -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu,
    Cantarell, sans-serif;
  padding: 20px;
}

.flashcard-container {
  perspective: 1000px;
  width: 100%;
  max-width: 400px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.flashcard {
  position: relative;
  width: 100%;
  height: 300px;
  transform-style: preserve-3d;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  cursor: pointer;
  border-radius: 20px;
}

.flashcard:hover {
  transform: scale(1.02);
}

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

.flashcard.flipped:hover {
  transform: rotateY(180deg) scale(1.02);
}

.flashcard-face {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  display: flex;
  justify-content: center;
  align-items: center;
  border-radius: 20px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
  padding: 40px;
  text-align: center;
}

.flashcard-front {
  background: linear-gradient(135deg, #ffffff 0%, #f5f5f5 100%);
  color: #2c3e50;
}

.flashcard-back {
  background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
  color: #ffffff;
  transform: rotateY(180deg);
}

.flashcard-content {
  font-size: 4rem;
  font-weight: 700;
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.1);
  animation: fadeIn 0.3s ease-in;
}

.flashcard-back .flashcard-content {
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

.flashcard-hint {
  position: absolute;
  bottom: 20px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 0.9rem;
  opacity: 0.6;
  font-style: italic;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: scale(0.95);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

/* Accessibility improvements */
.flashcard:focus {
  outline: 3px solid #667eea;
  outline-offset: 4px;
}

.flashcard:focus:not(:focus-visible) {
  outline: none;
}

.memorized-button {
  padding: 15px 30px;
  font-size: 1.1rem;
  font-weight: 600;
  color: white;
  background: linear-gradient(135deg, #10b981 0%, #059669 100%);
  border: none;
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(16, 185, 129, 0.3);
}

.memorized-button:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(16, 185, 129, 0.4);
  background: linear-gradient(135deg, #059669 0%, #047857 100%);
}

.memorized-button:active {
  transform: translateY(0);
  box-shadow: 0 2px 10px rgba(16, 185, 129, 0.3);
}

/* Responsive design */
@media (max-width: 480px) {
  .flashcard {
    height: 250px;
  }

  .flashcard-content {
    font-size: 3rem;
  }

  .flashcard-hint {
    font-size: 0.8rem;
  }

  .memorized-button {
    padding: 12px 24px;
    font-size: 1rem;
  }
}