/**
 * Alphabet Master - Professional UI/UX Styles
 * 
 * Modern design with smooth animations, responsive layout,
 * and accessibility features for multi-language support
 * 
 * @author LEARNature-ly Team
 * @version 1.0.0
 */

/* ============================================ */
/* CSS VARIABLES & THEME */
/* ============================================ */

:root {
  /* Colors - Professional Palette */
  --primary: #3b82f6;
  --primary-dark: #2563eb;
  --primary-light: #60a5fa;
  --secondary: #8b5cf6;
  --success: #10b981;
  --warning: #f59e0b;
  --error: #ef4444;
  --info: #06b6d4;

  /* Neutrals */
  --bg-primary: #ffffff;
  --bg-secondary: #f9fafb;
  --bg-tertiary: #f3f4f6;
  --text-primary: #111827;
  --text-secondary: #6b7280;
  --text-tertiary: #9ca3af;
  --border: #e5e7eb;
  --shadow: rgba(0, 0, 0, 0.1);

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

  /* Typography */
  --font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI",
    sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;
  --font-size-4xl: 2.5rem;
  --font-size-5xl: 3rem;

  /* Borders */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 350ms ease;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
  --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);

  /* Z-index layers */
  --z-base: 1;
  --z-dropdown: 10;
  --z-modal: 100;
  --z-overlay: 1000;
}

/* Dark mode support (optional) */
@media (prefers-color-scheme: dark) {
  :root {
    --bg-primary: #111827;
    --bg-secondary: #1f2937;
    --bg-tertiary: #374151;
    --text-primary: #f9fafb;
    --text-secondary: #d1d5db;
    --text-tertiary: #9ca3af;
    --border: #374151;
    --shadow: rgba(0, 0, 0, 0.3);
  }
}

/* ============================================ */
/* RESET & BASE STYLES */
/* ============================================ */

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

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  color: var(--text-primary);
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  overflow-x: hidden;
}

/* ============================================ */
/* APP CONTAINER */
/* ============================================ */

.app-container {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-lg);
}

/* ============================================ */
/* SCREEN LAYOUT */
/* ============================================ */

.screen {
  display: none;
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  animation: fadeIn 0.5s ease-out;
}

.screen.active {
  display: flex;
}

.screen-content {
  width: 100%;
  background: var(--bg-primary);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-2xl);
  padding: var(--spacing-2xl);
  animation: slideUp 0.5s ease-out;
}

/* ============================================ */
/* WELCOME SCREEN */
/* ============================================ */

.welcome-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
}

.logo-container {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
}

.logo-icon {
  font-size: var(--font-size-5xl);
  animation: bounce 2s infinite;
}

.logo-text {
  font-size: var(--font-size-3xl);
  font-weight: 800;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.tagline {
  font-size: var(--font-size-lg);
  color: var(--text-secondary);
  font-weight: 500;
}

/* ============================================ */
/* SECTION TITLE */
/* ============================================ */

.section-title {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--spacing-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
}

.title-icon {
  font-size: var(--font-size-3xl);
}

/* ============================================ */
/* LANGUAGE GRID */
/* ============================================ */

.language-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

.language-card {
  background: var(--bg-secondary);
  border: 2px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  text-align: center;
  cursor: pointer;
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

.language-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--accent-color, var(--primary));
  transform: scaleX(0);
  transition: transform var(--transition-base);
}

.language-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--accent-color, var(--primary));
}

.language-card:hover::before {
  transform: scaleX(1);
}

.language-card.selected {
  border-color: var(--accent-color, var(--primary));
  border-width: 3px;
  background: linear-gradient(135deg, var(--accent-color) 15, transparent);
  box-shadow: var(--shadow-xl);
}

.language-card.selected::before {
  transform: scaleX(1);
}

.language-icon {
  font-size: var(--font-size-5xl);
  margin-bottom: var(--spacing-md);
  animation: float 3s ease-in-out infinite;
}

.language-name {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--spacing-xs);
}

.language-native {
  font-size: var(--font-size-base);
  color: var(--text-secondary);
  margin-bottom: var(--spacing-sm);
}

.language-letters {
  font-size: var(--font-size-sm);
  color: var(--text-tertiary);
  font-weight: 500;
}

/* ============================================ */
/* SELECTED DISPLAY */
/* ============================================ */

.selected-display {
  background: linear-gradient(135deg, var(--success), #059669);
  color: white;
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
  animation: slideDown 0.3s ease-out;
}

.selected-language {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-md);
  font-size: var(--font-size-xl);
  font-weight: 600;
}

.selected-icon {
  font-size: var(--font-size-3xl);
}

.selected-check {
  font-size: var(--font-size-2xl);
  animation: scaleIn 0.3s ease-out;
}

/* ============================================ */
/* MODE GRID */
/* ============================================ */

.mode-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

.mode-card {
  background: var(--bg-secondary);
  border: 2px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  text-align: center;
  cursor: pointer;
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

.mode-card::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, var(--mode-color) 20, transparent);
  opacity: 0;
  transition: opacity var(--transition-base);
}

.mode-card:hover {
  transform: translateY(-4px) scale(1.02);
  box-shadow: var(--shadow-lg);
  border-color: var(--mode-color);
}

.mode-card:hover::before {
  opacity: 1;
}

.mode-card.selected {
  border-color: var(--mode-color);
  border-width: 3px;
  box-shadow: 0 0 0 4px rgba(var(--mode-color), 0.1);
}

.mode-card.selected::before {
  opacity: 1;
}

.mode-icon {
  font-size: var(--font-size-5xl);
  margin-bottom: var(--spacing-md);
}

.mode-name {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--spacing-sm);
}

.mode-description {
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
  line-height: 1.5;
}

.mode-badge {
  position: absolute;
  top: var(--spacing-sm);
  right: var(--spacing-sm);
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--font-size-xl);
  box-shadow: var(--shadow-md);
}

/* ============================================ */
/* DIFFICULTY GRID */
/* ============================================ */

.difficulty-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

.difficulty-card {
  background: var(--bg-secondary);
  border: 3px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--spacing-2xl);
  text-align: center;
  cursor: pointer;
  transition: all var(--transition-base);
  position: relative;
}

.difficulty-card::before {
  content: "";
  position: absolute;
  inset: -3px;
  border-radius: var(--radius-lg);
  padding: 3px;
  background: linear-gradient(135deg, var(--diff-color), transparent);
  -webkit-mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  opacity: 0;
  transition: opacity var(--transition-base);
}

.difficulty-card:hover {
  transform: scale(1.05);
  box-shadow: var(--shadow-lg);
}

.difficulty-card:hover::before {
  opacity: 1;
}

.difficulty-card.selected {
  border-color: var(--diff-color);
  background: linear-gradient(
    135deg,
    var(--diff-color) 15,
    var(--bg-secondary)
  );
  box-shadow: 0 0 0 4px rgba(var(--diff-color), 0.1);
}

.difficulty-card.selected::before {
  opacity: 1;
}

.difficulty-icon {
  font-size: var(--font-size-5xl);
  margin-bottom: var(--spacing-md);
}

.difficulty-name {
  font-size: var(--font-size-2xl);
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: var(--spacing-sm);
}

.difficulty-desc {
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
}

/* ============================================ */
/* BUTTONS */
/* ============================================ */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: var(--font-size-base);
  font-weight: 600;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-base);
  text-decoration: none;
  font-family: inherit;
  white-space: nowrap;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none !important;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-primary:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-primary:active:not(:disabled) {
  transform: translateY(0);
}

.btn-success {
  background: linear-gradient(135deg, var(--success), #059669);
  color: white;
  box-shadow: var(--shadow-md);
}

.btn-success:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 2px solid var(--border);
}

.btn-secondary:hover:not(:disabled) {
  background: var(--bg-secondary);
  border-color: var(--text-tertiary);
}

.btn-large {
  padding: var(--spacing-lg) var(--spacing-2xl);
  font-size: var(--font-size-lg);
  width: 100%;
  margin-top: var(--spacing-lg);
}

.btn-icon {
  font-size: var(--font-size-xl);
}

.btn.pulse {
  animation: pulse 2s infinite;
}

/* ============================================ */
/* BACK BUTTON */
/* ============================================ */

.back-btn {
  background: var(--bg-tertiary);
  border: none;
  border-radius: var(--radius-md);
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: var(--font-size-base);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-base);
  margin-bottom: var(--spacing-lg);
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.back-btn:hover {
  background: var(--bg-secondary);
  color: var(--text-primary);
  transform: translateX(-4px);
}

/* ============================================ */
/* GAME SCREEN */
/* ============================================ */

.game-container {
  width: 100%;
  max-width: 900px;
  margin: 0 auto;
}

.game-header-bar {
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
  display: flex;
  justify-content: space-between;
  align-items: center;
  box-shadow: var(--shadow-sm);
}

.game-info-display {
  display: flex;
  gap: var(--spacing-lg);
  flex-wrap: wrap;
}

.game-info-display > span {
  font-size: var(--font-size-sm);
  font-weight: 600;
  padding: var(--spacing-xs) var(--spacing-md);
  background: var(--bg-primary);
  border-radius: var(--radius-sm);
}

.game-controls {
  display: flex;
  gap: var(--spacing-sm);
}

.control-btn {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  border: 2px solid var(--border);
  background: var(--bg-primary);
  font-size: var(--font-size-lg);
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

.control-btn:hover {
  transform: scale(1.1);
  box-shadow: var(--shadow-md);
}

.control-btn.danger:hover {
  border-color: var(--error);
  background: var(--error);
  color: white;
}

/* ============================================ */
/* PROGRESS BAR */
/* ============================================ */

.progress-container {
  margin-bottom: var(--spacing-xl);
  position: relative;
}

.progress-bar-bg {
  height: 12px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-full);
  overflow: hidden;
  position: relative;
}

.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  border-radius: var(--radius-full);
  width: 0%;
  transition: width 0.5s ease-out;
  position: relative;
  overflow: hidden;
}

.progress-bar-fill::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  background: linear-gradient(
    90deg,
    rgba(255, 255, 255, 0) 0%,
    rgba(255, 255, 255, 0.3) 50%,
    rgba(255, 255, 255, 0) 100%
  );
  animation: shimmer 2s infinite;
}

.progress-text {
  text-align: center;
  font-weight: 700;
  color: var(--text-secondary);
  margin-top: var(--spacing-sm);
  font-size: var(--font-size-sm);
}

/* ============================================ */
/* STREAK DISPLAY */
/* ============================================ */

.streak-display {
  position: fixed;
  top: 20%;
  left: 50%;
  transform: translateX(-50%);
  z-index: var(--z-dropdown);
  pointer-events: none;
}

.streak-badge {
  background: linear-gradient(135deg, var(--warning), #dc2626);
  color: white;
  padding: var(--spacing-md) var(--spacing-xl);
  border-radius: var(--radius-full);
  font-size: var(--font-size-xl);
  font-weight: 800;
  box-shadow: var(--shadow-xl);
}

/* ============================================ */
/* LETTER DISPLAY */
/* ============================================ */

.letter-display-container {
  background: linear-gradient(135deg, var(--primary) 10, var(--secondary) 10);
  border-radius: var(--radius-xl);
  padding: var(--spacing-2xl);
  margin-bottom: var(--spacing-xl);
  min-height: 300px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.letter-card {
  text-align: center;
}

.letter-main {
  font-size: 10rem;
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: var(--spacing-lg);
  text-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
  line-height: 1;
}

.letter-card.rtl .letter-main {
  direction: rtl;
}

.letter-image {
  max-width: 200px;
  height: auto;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  animation: fadeIn 0.5s ease-out 0.2s both;
}

/* ============================================ */
/* QUESTION PROMPT */
/* ============================================ */

.question-prompt {
  text-align: center;
  margin-bottom: var(--spacing-xl);
}

.question-text {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  color: var(--text-primary);
}

/* ============================================ */
/* OPTIONS GRID */
/* ============================================ */

.options-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-xl);
}

.option-btn {
  background: var(--bg-secondary);
  border: 3px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  cursor: pointer;
  transition: all var(--transition-base);
  font-family: inherit;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-sm);
}

.option-btn:hover:not(:disabled) {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--primary);
}

.option-btn:disabled {
  cursor: not-allowed;
}

.option-letter {
  font-size: var(--font-size-4xl);
  font-weight: 800;
  color: var(--text-primary);
}

.option-letter.rtl {
  direction: rtl;
}

.option-name {
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
  font-weight: 600;
}

.option-btn.correct {
  border-color: var(--success);
  background: linear-gradient(135deg, var(--success) 20, var(--bg-secondary));
  animation: correctShake 0.5s ease-out;
}

.option-btn.incorrect {
  border-color: var(--error);
  background: linear-gradient(135deg, var(--error) 20, var(--bg-secondary));
  animation: incorrectShake 0.5s ease-out;
}

/* ============================================ */
/* RESULTS SCREEN */
/* ============================================ */

.results-wrapper {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
}

.results-header {
  margin-bottom: var(--spacing-xl);
}

.results-title {
  font-size: var(--font-size-3xl);
  font-weight: 800;
  margin-bottom: var(--spacing-sm);
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.results-lang {
  font-size: var(--font-size-lg);
  color: var(--text-secondary);
  font-weight: 600;
}

.results-score-card {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: white;
  border-radius: var(--radius-xl);
  padding: var(--spacing-2xl);
  margin-bottom: var(--spacing-xl);
  position: relative;
  overflow: hidden;
}

.results-score-card::before {
  content: "";
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(
    circle,
    rgba(255, 255, 255, 0.1) 0%,
    transparent 70%
  );
  animation: rotate 10s linear infinite;
}

.score-main {
  font-size: var(--font-size-5xl);
  font-weight: 900;
  margin-bottom: var(--spacing-sm);
  position: relative;
  z-index: 1;
}

.score-label {
  font-size: var(--font-size-lg);
  font-weight: 600;
  opacity: 0.9;
  position: relative;
  z-index: 1;
}

.grade-badge {
  display: inline-block;
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: var(--radius-full);
  font-size: var(--font-size-xl);
  font-weight: 800;
  margin-top: var(--spacing-md);
  background: rgba(255, 255, 255, 0.2);
  backdrop-filter: blur(10px);
  position: relative;
  z-index: 1;
}

.results-stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

.stat-item {
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  text-align: center;
}

.stat-icon {
  font-size: var(--font-size-3xl);
  margin-bottom: var(--spacing-sm);
}

.stat-value {
  font-size: var(--font-size-2xl);
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: var(--spacing-xs);
}

.stat-label {
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
  font-weight: 600;
}

.results-time {
  display: flex;
  justify-content: center;
  gap: var(--spacing-xl);
  font-size: var(--font-size-base);
  color: var(--text-secondary);
  font-weight: 600;
  margin-bottom: var(--spacing-xl);
}

.results-actions {
  display: flex;
  gap: var(--spacing-md);
  flex-wrap: wrap;
  margin-bottom: var(--spacing-2xl);
}

.results-actions .btn {
  flex: 1;
  min-width: 200px;
}

/* ============================================ */
/* FEATURES GRID */
/* ============================================ */

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--spacing-md);
  margin-top: var(--spacing-2xl);
}

.feature-item {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-md);
  background: var(--bg-secondary);
  border-radius: var(--radius-md);
}

.feature-icon {
  font-size: var(--font-size-2xl);
}

.feature-text {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--text-secondary);
}

/* ============================================ */
/* LOADING & MODALS */
/* ============================================ */

.loading-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(8px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: var(--z-overlay);
  animation: fadeIn 0.3s ease-out;
}

.loading-spinner {
  width: 64px;
  height: 64px;
  border: 6px solid rgba(255, 255, 255, 0.2);
  border-top-color: white;
  border-radius: var(--radius-full);
  animation: spin 1s linear infinite;
  margin-bottom: var(--spacing-lg);
}

.loading-text {
  color: white;
  font-size: var(--font-size-xl);
  font-weight: 600;
}

/* Feedback Toast */
.feedback-toast {
  position: fixed;
  top: var(--spacing-xl);
  right: var(--spacing-xl);
  padding: var(--spacing-lg) var(--spacing-xl);
  border-radius: var(--radius-lg);
  font-weight: 600;
  box-shadow: var(--shadow-xl);
  transform: translateX(400px);
  transition: transform var(--transition-base);
  z-index: var(--z-modal);
}

.feedback-toast.show {
  transform: translateX(0);
}

.feedback-toast.success {
  background: var(--success);
  color: white;
}

.feedback-toast.error {
  background: var(--error);
  color: white;
}

.feedback-toast.info {
  background: var(--info);
  color: white;
}

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

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeInScale {
  from {
    opacity: 0;
    transform: scale(0.8);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

@keyframes scaleIn {
  from {
    transform: scale(0);
  }
  to {
    transform: scale(1);
  }
}

@keyframes bounce {
  0%,
  100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-10px);
  }
}

@keyframes float {
  0%,
  100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-8px);
  }
}

@keyframes pulse {
  0%,
  100% {
    box-shadow: 0 0 0 0 rgba(59, 130, 246, 0.7);
  }
  50% {
    box-shadow: 0 0 0 12px rgba(59, 130, 246, 0);
  }
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

@keyframes shimmer {
  0% {
    transform: translateX(-100%);
  }
  100% {
    transform: translateX(100%);
  }
}

@keyframes correctShake {
  0%,
  100% {
    transform: translateX(0);
  }
  25% {
    transform: translateX(-10px) scale(1.1);
  }
  75% {
    transform: translateX(10px) scale(1.1);
  }
}

@keyframes incorrectShake {
  0%,
  100% {
    transform: translateX(0);
  }
  20%,
  60% {
    transform: translateX(-10px);
  }
  40%,
  80% {
    transform: translateX(10px);
  }
}

@keyframes bounceIn {
  from {
    opacity: 0;
    transform: scale(0.3);
  }
  50% {
    transform: scale(1.05);
  }
  70% {
    transform: scale(0.9);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

@keyframes rotate {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

/* ============================================ */
/* RESPONSIVE DESIGN */
/* ============================================ */

@media (max-width: 768px) {
  .screen-content {
    padding: var(--spacing-lg);
  }

  .logo-text {
    font-size: var(--font-size-2xl);
  }

  .language-grid,
  .mode-grid,
  .difficulty-grid {
    grid-template-columns: 1fr;
  }

  .letter-main {
    font-size: 6rem;
  }

  .options-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .results-actions {
    flex-direction: column;
  }

  .results-actions .btn {
    width: 100%;
  }

  .game-header-bar {
    flex-direction: column;
    gap: var(--spacing-md);
  }

  .feedback-toast {
    right: var(--spacing-md);
    left: var(--spacing-md);
  }
}

@media (max-width: 480px) {
  .app-container {
    padding: var(--spacing-sm);
  }

  .section-title {
    font-size: var(--font-size-xl);
  }

  .letter-main {
    font-size: 4rem;
  }

  .options-grid {
    grid-template-columns: 1fr;
  }
}

/* ============================================ */
/* ACCESSIBILITY */
/* ============================================ */

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* Focus visible for keyboard navigation */
*:focus-visible {
  outline: 3px solid var(--primary);
  outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  :root {
    --border: #000000;
  }

  .btn {
    border: 2px solid currentColor;
  }
}