/**
 * Flashcards System CSS
 * 3D Card flip animation with spaced repetition UI
 */

/* ==========================================================================
   CSS CUSTOM PROPERTIES
   ========================================================================== */

:root {
  /**
   * Flashcard colors
   */
  --fc-primary: #28a745;
  --fc-primary-dark: #218838;
  --fc-primary-light: #48c765;
  --fc-accent: #17a2b8;
  --fc-accent-light: #5cdbdf;
  --fc-warning: #ffc107;
  --fc-warning-dark: #e0a800;
  --fc-error: #dc3545;
  --fc-success: #28a745;
  --fc-info: #17a2b8;

  /**
   * Text colors
   */
  --fc-text-primary: #212529;
  --fc-text-secondary: #6c757d;
  --fc-text-muted: #adb5bd;
  --fc-text-inverse: #ffffff;

  /**
   * Background colors
   */
  --fc-bg-primary: #ffffff;
  --fc-bg-secondary: #f8f9fa;
  --fc-bg-tertiary: #e9ecef;
  --fc-bg-card: #ffffff;
  --fc-bg-shadow: rgba(0, 0, 0, 0.1);
  --fc-gradient-start: #28a745;
  --fc-gradient-end: #34dcb3;

  /**
   * Border colors
   */
  --fc-border-light: #dee2e6;
  --fc-border-medium: #ced4da;
  --fc-border-dark: #868e96;
  --fc-border-focus: #80bdff;

  /**
   * Spacing tokens
   */
  --fc-spacing-xs: 0.25rem;
  --fc-spacing-sm: 0.5rem;
  --fc-spacing-md: 1rem;
  --fc-spacing-lg: 1.5rem;
  --fc-spacing-xl: 2rem;
  --fc-spacing-2xl: 3rem;

  /**
   * Border radius
   */
  --fc-radius-sm: 0.25rem;
  --fc-radius-md: 0.5rem;
  --fc-radius-lg: 1rem;
  --fc-radius-xl: 1.5rem;
  --fc-radius-full: 9999px;

  /**
   * Shadows
   */
  --fc-shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
  --fc-shadow-md: 0 4px 16px rgba(0, 0, 0, 0.15);
  --fc-shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.2);
  --fc-shadow-hover: 0 12px 40px rgba(0, 0, 0, 0.25);

  /**
   * Typography
   */
  --fc-font-family-base:
    -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --fc-font-family-mono: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
  --fc-font-size-xs: 0.75rem;
  --fc-font-size-sm: 0.875rem;
  --fc-font-size-base: 1rem;
  --fc-font-size-lg: 1.125rem;
  --fc-font-size-xl: 1.25rem;
  --fc-font-size-2xl: 1.5rem;
  --fc-font-size-3xl: 1.875rem;

  /**
   * Transitions
   */
  --fc-transition-fast: 150ms ease;
  --fc-transition-base: 200ms ease;
  --fc-transition-slow: 300ms ease;

  /**
   * 3D transform
   */
  --fc-preserve-3d: preserve-3d;
  --fc-backface-hidden: hidden;
}

/* Dark mode */
@media (prefers-color-scheme: dark) {
  :root {
    --fc-text-primary: #f8f9fa;
    --fc-text-secondary: #adb5bd;
    --fc-text-muted: #6c757d;
    --fc-text-inverse: #212529;

    --fc-bg-primary: #1a1a2e;
    --fc-bg-secondary: #16213e;
    --fc-bg-tertiary: #0f3460;
    --fc-bg-card: #1a1a2e;
    --fc-bg-shadow: rgba(0, 0, 0, 0.3);
  }
}

/* ==========================================================================
   FLASHCARD CONTAINER
   ========================================================================== */

/**
 * Main container
 * .flashcard__container
 */
.flashcard-container {
  max-width: 600px;
  margin: 0 auto;
  padding: var(--fc-spacing-xl);
  perspective: 1000px;
  animation: fadeIn var(--fc-transition-slow) ease-out;
}

/**
 * Deck selection
 * .flashcard__deck-selector
 */
.flashcard-deck-selector {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: var(--fc-spacing-md);
  margin-bottom: var(--fc-spacing-xl);
}

/**
 * Deck card
 * .flashcard__deck-card
 */
.flashcard-deck-card {
  background: var(--fc-bg-card);
  border: 1px solid var(--fc-border-light);
  border-radius: var(--fc-radius-lg);
  padding: var(--fc-spacing-lg);
  cursor: pointer;
  transition: all var(--fc-transition-base);
  box-shadow: var(--fc-shadow-sm);
}

.flashcard-deck-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--fc-shadow-md);
  border-color: var(--fc-primary);
}

.flashcard-deck-card.active {
  border-color: var(--fc-primary);
  box-shadow: 0 0 0 3px rgba(40, 167, 69, 0.2);
}

/**
 * Card flip area
 * .flashcard__area
 */
.flashcard-area {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--fc-spacing-lg);
}

/**
 * Flip container (3D)
 * .flashcard__flip-container
 */
.flashcard-flip-container {
  position: relative;
  width: 100%;
  aspect-ratio: 3/2;
  max-height: 400px;
  cursor: pointer;
  perspective: 1000px;
}

/**
 * Inner flip wrapper
 * .flashcard__flip-inner
 */
.flashcard-flip-inner {
  position: relative;
  width: 100%;
  height: 100%;
  text-align: center;
  transition: transform var(--fc-transition-slow);
  transform-style: var(--fc-preserve-3d);
}

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

/**
 * Card faces
 * .flashcard__face
 */
.flashcard-face {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: var(--fc-backface-hidden);
  -webkit-backface-visibility: var(--fc-backface-hidden);
  border-radius: var(--fc-radius-lg);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: var(--fc-spacing-xl);
  box-shadow: var(--fc-shadow-md);
  background: linear-gradient(135deg, var(--fc-bg-card), var(--fc-bg-secondary));
  border: 2px solid var(--fc-border-light);
}

/**
 * Front face (question)
 * .flashcard__face--front
 */
.flashcard-face--front {
  transform: rotateY(0deg);
}

/**
 * Back face (answer)
 * .flashcard__face--back
 */
.flashcard-face--back {
  transform: rotateY(180deg);
  background: linear-gradient(135deg, var(--fc-gradient-start), var(--fc-gradient-end));
  color: var(--fc-text-inverse);
  border-color: var(--fc-primary);
}

/**
 * Face content
 * .flashcard__face-content
 */
.flashcard-face-content {
  font-size: var(--fc-font-size-xl);
  line-height: 1.6;
  color: var(--fc-text-primary);
}

.flashcard-face--back .flashcard-face-content {
  color: var(--fc-text-inverse);
}

/* ==========================================================================
   CARD STATUS INDICATORS
   ========================================================================== */

/**
 * Progress bar
 * .flashcard__progress-bar
 */
.flashcard-progress-bar {
  width: 100%;
  max-width: 400px;
  height: 8px;
  background: var(--fc-bg-tertiary);
  border-radius: var(--fc-radius-full);
  overflow: hidden;
}

.flashcard-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--fc-primary), var(--fc-accent));
  transition: width var(--fc-transition-slow);
}

/**
 * Progress indicators
 * .flashcard__stats
 */
.flashcard-stats {
  display: flex;
  flex-wrap: wrap;
  gap: var(--fc-spacing-md);
  justify-content: center;
  font-size: var(--fc-font-size-sm);
}

.flashcard-stat {
  display: flex;
  align-items: center;
  gap: var(--fc-spacing-xs);
  background: var(--fc-bg-secondary);
  padding: var(--fc-spacing-xs) var(--fc-spacing-sm);
  border-radius: var(--fc-radius-full);
  color: var(--fc-text-secondary);
}

.flashcard-stat--mastered {
  color: var(--fc-success);
}

.flashcard-stat--due {
  color: var(--fc-warning-dark);
}

.flashcard-stat--new {
  color: var(--fc-info);
}

/* ==========================================================================
   NAVIGATION CONTROLS
   ========================================================================== */

/**
 * Navigation buttons
 * .flashcard__nav-controls
 */
.flashcard-nav-controls {
  display: flex;
  justify-content: center;
  gap: var(--fc-spacing-md);
  flex-wrap: wrap;
}

/**
 * Navigation buttons
 * .flashcard__nav-btn
 */
.flashcard-nav-btn {
  padding: var(--fc-spacing-md) var(--fc-spacing-xl);
  font-size: var(--fc-font-size-base);
  font-weight: 600;
  border: none;
  border-radius: var(--fc-radius-full);
  cursor: pointer;
  transition: all var(--fc-transition-fast);
  background: var(--fc-bg-tertiary);
  color: var(--fc-text-primary);
}

.flashcard-nav-btn:hover {
  background: var(--fc-primary);
  color: var(--fc-text-inverse);
  transform: translateY(-2px);
  box-shadow: var(--fc-shadow-sm);
}

.flashcard-nav-btn:active {
  transform: translateY(0);
}

.flashcard-nav-btn:focus {
  outline: none;
  box-shadow: 0 0 0 3px var(--fc-border-focus);
}

.flashcard-nav-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

/**
 * Primary action buttons
 * .flashcard__action-btn
 */
.flashcard-action-btn {
  padding: var(--fc-spacing-md) var(--fc-spacing-xl);
  font-size: var(--fc-font-size-base);
  font-weight: 600;
  border: none;
  border-radius: var(--fc-radius-full);
  cursor: pointer;
  transition: all var(--fc-transition-fast);
  background: var(--fc-primary);
  color: var(--fc-text-inverse);
}

.flashcard-action-btn:hover {
  background: var(--fc-primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--fc-shadow-md);
}

.flashcard-action-btn:active {
  transform: translateY(0);
}

/* ==========================================================================
   RATINGS (spaced repetition)
   ========================================================================== */

/**
 * Rating section
 * .flashcard__ratings
 */
.flashcard-ratings {
  display: flex;
  justify-content: center;
  gap: var(--fc-spacing-md);
  flex-wrap: wrap;
}

/**
 * Rating buttons
 * .flashcard__rating-btn
 */
.flashcard-rating-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: var(--fc-spacing-md);
  border: 2px solid var(--fc-border-light);
  border-radius: var(--fc-radius-lg);
  cursor: pointer;
  transition: all var(--fc-transition-fast);
  background: var(--fc-bg-card);
  min-width: 100px;
}

.flashcard-rating-btn:hover {
  border-color: var(--fc-primary);
  transform: translateY(-4px);
  box-shadow: var(--fc-shadow-md);
}

.flashcard-rating-btn:focus {
  outline: none;
  box-shadow: 0 0 0 3px var(--fc-border-focus);
}

/**
 * Rating emoji icon
 * .flashcard__rating-icon
 */
.flashcard-rating-icon {
  font-size: var(--fc-font-size-2xl);
  margin-bottom: var(--fc-spacing-xs);
}

/**
 * Rating label
 * .flashcard__rating-label
 */
.flashcard-rating-label {
  font-size: var(--fc-font-size-xs);
  font-weight: 600;
  color: var(--fc-text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

/* Easy */
.flashcard-rating-btn[data-quality='0'] .flashcard-rating-icon {
  content: 💀;
}

/* Medium */
.flashcard-rating-btn[data-quality='1'] .flashcard-rating-icon {
  content: 😐;
}

/* Good */
.flashcard-rating-btn[data-quality='2'] .flashcard-rating-icon {
  content: 🙂;
}

/* ==========================================================================
   KEYBOARD HINTS
   ========================================================================== */

/**
 * Keyboard hint
 * .flashcard__keyboard-hint
 */
.flashcard-keyboard-hint {
  font-size: var(--fc-font-size-xs);
  color: var(--fc-text-muted);
  text-align: center;
  padding: var(--fc-spacing-sm);
  background: var(--fc-bg-secondary);
  border-radius: var(--fc-radius-sm);
}

/**
 * Keyboard key
 * .flashcard__key
 */
.flashcard-key {
  display: inline-block;
  padding: 0 var(--fc-spacing-xs);
  padding: calc(var(--fc-spacing-xs) / 2) var(--fc-spacing-sm);
  border: 1px solid var(--fc-border-medium);
  border-radius: var(--fc-radius-sm);
  font-family: var(--fc-font-family-mono);
  font-size: var(--fc-font-size-xs);
  background: var(--fc-bg-tertiary);
  margin: 0 var(--fc-spacing-xs);
}

/* ==========================================================================
   EMPTY STATE
   ========================================================================== */

/**
 * Empty state
 * .flashcard__empty-state
 */
.flashcard-empty-state {
  text-align: center;
  padding: var(--fc-spacing-2xl);
}

.flashcard-empty-icon {
  font-size: 4rem;
  margin-bottom: var(--fc-spacing-lg);
}

.flashcard-empty-title {
  font-size: var(--fc-font-size-2xl);
  color: var(--fc-text-primary);
  margin-bottom: var(--fc-spacing-md);
}

.flashcard-empty-text {
  font-size: var(--fc-font-size-base);
  color: var(--fc-text-secondary);
  margin-bottom: var(--fc-spacing-lg);
}

/* ==========================================================================
   ANIMATIONS
   ========================================================================== */

/**
 * Fade in
 */
@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

/**
 * Slide up
 */
@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/**
 * Card flip animation
 */
@keyframes flipCard {
  0% {
    transform: rotateX(0);
  }
  50% {
    transform: rotateX(90deg);
  }
  100% {
    transform: rotateX(0);
  }
}

/**
 * Pulse animation
 */
@keyframes pulse {
  0%,
  100% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.05);
  }
}

/**
 * Shake animation (for incorrect)
 */
@keyframes shake {
  0%,
  100% {
    transform: translateX(0);
  }
  10%,
  30%,
  50%,
  70%,
  90% {
    transform: translateX(-5px);
  }
  20%,
  40%,
  60%,
  80% {
    transform: translateX(5px);
  }
}

/* ==========================================================================
   RESPONSIVE BREAKPOINTS
   ========================================================================== */

/**
 * Mobile (280px+)
 */
@media screen and (min-width: 280px) {
  .flashcard-container {
    padding: var(--fc-spacing-lg);
  }

  .flashcard-stats {
    justify-content: center;
  }

  .flashcard-ratings {
    flex-direction: row;
    flex-wrap: wrap;
  }
}

/**
 * Tablet (768px+)
 */
@media screen and (min-width: 768px) {
  .flashcard-area {
    gap: var(--fc-spacing-xl);
  }

  .flashcard-stats {
    justify-content: flex-start;
  }

  .flashcard-nav-controls {
    justify-content: space-between;
  }
}

/**
 * Desktop (1024px+)
 */
@media screen and (min-width: 1024px) {
  .flashcard-container {
    padding: var(--fc-spacing-2xl);
  }

  .flashcard-flip-container {
    max-height: 500px;
  }
}

/* ==========================================================================
   REDUCED MOTION
   ========================================================================== */

@media (prefers-reduced-motion: reduce) {
  .flashcard-flip-inner,
  .flashcard-deck-card,
  .flashcard-action-btn,
  .flashcard-rating-btn {
    transition: none;
  }
}

/* ==========================================================================
   END OF STYLES
   ========================================================================== */