/* Flashcard Container */
.flashcard-container {
  width: 100%;
  min-height: calc(100vh - 64px);
  padding: var(--space-4) var(--space-3);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: var(--space-4);
  background: var(--bg-secondary);
  position: relative;
}

/* Flashcard Squircle Look */
.flashcard {
  width: min(640px, 100%);
  min-height: 420px;
  margin: 0 auto;
  max-width: 640px;
  perspective: 1400px;
  position: relative;
  transform-style: preserve-3d;
  transition: transform var(--ms-duration-normal) var(--ms-curve-spring);
  cursor: pointer;
}

.flashcard:active {
  transform: scale(0.98);
}

@media (max-width: 640px) {
  .flashcard {
    min-height: 380px;
  }
}

.flashcard-side {
  width: 100%;
  height: 100%;
  position: absolute;
  backface-visibility: hidden;
  background: var(--card-bg);
  border-radius: 28px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.12), 0 8px 16px rgba(0, 0, 0, 0.08);
  padding: var(--space-5);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  transition: transform var(--ms-duration-slow) cubic-bezier(0.4, 0, 0.2, 1);
  border: 1px solid rgba(0, 0, 0, 0.05);
  overflow: hidden;
}

[data-theme='dark'] .flashcard-side {
  border: 1px solid rgba(255, 255, 255, 0.1);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.3), 0 8px 16px rgba(0, 0, 0, 0.2);
}

.flashcard-front {
  transform: rotateY(0deg);
  z-index: 2;
}

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

/* Flip Animation */
.flashcard.flipped .flashcard-front {
  transform: rotateY(-180deg);
}

.flashcard.flipped .flashcard-back {
  transform: rotateY(0deg);
  z-index: 2;
}

/* Card Content Typography */
.word {
  font-size: clamp(32px, 5vw, 40px);
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  margin-bottom: var(--space-1);
  line-height: 1.1;
}

.phonetic {
  font-size: 20px;
  color: var(--text-secondary);
  font-weight: 500;
  margin-bottom: var(--space-4);
}

/* Meaningful Transitions */
@keyframes cardSlideIn {
  from { opacity: 0; transform: translateX(30px) scale(0.98); }
  to { opacity: 1; transform: translateX(0) scale(1); }
}

.flashcard-view.next-card {
  animation: cardSlideIn var(--ms-duration-normal) var(--ms-curve-spring);
}

/* Rating Buttons as iOS Controls */
.rating-buttons {
  margin-top: auto;
  padding-top: var(--space-3);
}

.btn-group {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-2);
}

.btn-rating {
  min-height: 72px;
  border-radius: 16px;
  border: 1.5px solid rgba(60, 60, 67, 0.15);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  transition: all var(--ms-duration-fast) var(--ms-curve-default);
  background: var(--bg-secondary);
  font-weight: 600;
  position: relative;
  overflow: hidden;
}

.btn-rating::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: currentColor;
  opacity: 0;
  transition: opacity var(--ms-duration-fast);
}

.btn-rating:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  border-color: currentColor;
}

.btn-rating:hover::before {
  opacity: 0.05;
}

.btn-rating:active {
  transform: translateY(0) scale(0.96);
}

@media (max-width: 640px) {
  .flashcard {
    min-height: 320px;
  }
  .btn-group {
    grid-template-columns: 1fr;
  }
}

.btn-again { 
  color: var(--danger-color); 
  background: rgba(255, 59, 48, 0.08); 
}
.btn-again:hover {
  background: rgba(255, 59, 48, 0.12);
}

.btn-hard { 
  color: var(--warning-color); 
  background: rgba(255, 149, 0, 0.08); 
}
.btn-hard:hover {
  background: rgba(255, 149, 0, 0.12);
}

.btn-good { 
  color: var(--accent-color); 
  background: rgba(52, 199, 89, 0.08); 
}
.btn-good:hover {
  background: rgba(52, 199, 89, 0.12);
}

.btn-easy { 
  color: var(--primary-color); 
  background: rgba(0, 122, 255, 0.08); 
}
.btn-easy:hover {
  background: rgba(0, 122, 255, 0.12);
}

.rating-label {
  font-weight: 600;
  font-size: var(--fs-body);
  position: relative;
  z-index: 1;
}

.rating-interval {
  font-size: 11px;
  font-weight: 500;
  opacity: 0.7;
  position: relative;
  z-index: 1;
}

/* Keyboard Shortcuts Hint */
.shortcuts-hint {
  position: fixed;
  bottom: 20px;
  right: 20px;
  background: var(--bg-secondary);
  padding: 16px;
  border-radius: 12px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
  font-size: 13px;
  color: var(--text-secondary);
}

.shortcuts-hint kbd {
  background: var(--bg-primary);
  padding: 2px 6px;
  border-radius: 4px;
  font-family: monospace;
  font-weight: 600;
  margin: 0 2px;
}

/* Session Info */
.session-info {
  display: flex;
  align-items: center;
  gap: 16px;
  min-width: 200px;
  width: 100%;
  max-width: 640px;
}

.card-counter {
  font-size: 14px;
  font-weight: 600;
  color: var(--text-secondary);
  white-space: nowrap;
  min-width: 60px;
}

.progress-bar {
  flex: 1;
  height: 6px;
  background: var(--bg-primary);
  border-radius: 10px;
  overflow: hidden;
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.05);
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-color), #5856D6);
  transition: width 0.3s var(--ms-curve-default);
  border-radius: 10px;
}

/* Mode Selection */
.mode-selection {
  text-align: center;
}

.stats-summary {
  display: flex;
  justify-content: center;
  gap: var(--space-3);
  margin: var(--space-5) 0;
}

.stat-card {
  background: var(--card-bg);
  padding: var(--space-4);
  border-radius: 20px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.08);
  min-width: 120px;
  text-align: center;
  border: 1px solid rgba(0, 0, 0, 0.05);
  transition: transform var(--ms-duration-fast), box-shadow var(--ms-duration-fast);
}

.stat-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.12);
}

[data-theme='dark'] .stat-card {
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.stat-number {
  font-size: var(--fs-h1);
  font-weight: 700;
  color: var(--primary-color);
  letter-spacing: -0.02em;
}

.stat-label {
  font-size: var(--fs-caption);
  color: var(--text-secondary);
  margin-top: 4px;
}

.mode-buttons {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  max-width: 320px;
  margin: 0 auto;
}

/* Session Complete */
.session-complete {
  text-align: center;
}

.complete-animation {
  font-size: 64px;
  margin-bottom: var(--space-3);
}

.session-stats {
  display: flex;
  justify-content: center;
  gap: var(--space-5);
  margin: var(--space-5) 0;
}

.stat-item .stat-value {
  font-size: var(--fs-h2);
  font-weight: 700;
  color: var(--text-primary);
}

.stat-item .stat-label {
  font-size: var(--fs-caption);
  color: var(--text-secondary);
}

.mastery-progress {
  max-width: 400px;
  margin: 0 auto var(--space-5);
}

.mastery-bar {
  height: 8px;
  background: var(--bg-secondary);
  border-radius: 10px;
  margin: var(--space-2) 0;
  overflow: hidden;
}

.mastery-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
  transition: width 1.2s var(--ms-curve-spring);
}

.action-buttons {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  max-width: 320px;
  margin: 0 auto;
  width: 100%;
}

.action-buttons .btn {
  width: 100%;
  text-align: center;
  padding: var(--space-3);
  border-radius: 16px;
  font-weight: 600;
  font-size: var(--fs-body);
  transition: all var(--ms-duration-fast) var(--ms-curve-default);
}

.action-buttons .btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.action-buttons .btn:active {
  transform: translateY(0) scale(0.98);
}

/* Session Controls */
.session-controls {
  margin-top: var(--space-4);
  display: flex;
  justify-content: center;
  gap: var(--space-3);
  align-items: center;
  flex-wrap: wrap;
}

.btn-reveal {
  margin-top: auto;
  background: var(--primary-color);
  color: #ffffff;
  padding: var(--space-2);
  border-radius: 16px;
  font-size: var(--fs-h3);
  width: 100%;
  height: 56px;
  box-shadow: 0 8px 20px rgba(0, 122, 255, 0.25);
  border: none;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--ms-duration-fast) var(--ms-curve-default);
}

.btn-reveal:hover {
  background: #0056b3;
  box-shadow: 0 10px 24px rgba(0, 122, 255, 0.3);
  transform: translateY(-1px);
}

.btn-reveal:active {
  transform: translateY(0) scale(0.98);
}