/* ==========================================================================
   VerbaTube Dark Theme - Minimalist + Coral Accent + Duolingo-Inspired
   ========================================================================== */

/* --------------------------------------------------------------------------
   1. CSS Custom Properties (Variables)
   -------------------------------------------------------------------------- */
:root {
  /* Backgrounds */
  --bg-primary: #0D0D0F;
  --bg-secondary: #1A1A1E;
  --bg-tertiary: #252529;
  --bg-elevated: #2A2A30;

  /* Accent Colors */
  --coral: #FF6B4A;
  --coral-hover: #FF8566;
  --coral-pressed: #E55A3C;
  --coral-glow: rgba(255, 107, 74, 0.15);
  --coral-glow-strong: rgba(255, 107, 74, 0.35);

  /* Text Colors */
  --text-primary: #FFFFFF;
  --text-secondary: #B8B8C0;
  --text-muted: #6B6B75;
  --text-inverse: #0D0D0F;

  /* Semantic Colors */
  --success: #4ADE80;
  --success-bg: #134E32;
  --success-glow: rgba(74, 222, 128, 0.15);
  --error: #F87171;
  --error-bg: #5C1D1D;
  --error-glow: rgba(248, 113, 113, 0.15);
  --warning: #FBBF24;
  --warning-bg: #533C10;
  --warning-glow: rgba(251, 191, 36, 0.15);
  --info: #38BDF8;
  --info-bg: #0C3D5C;
  --info-glow: rgba(56, 189, 248, 0.15);

  /* Gamification */
  --xp-gold: #FFD700;
  --streak-orange: #FF9500;
  --level-purple: #A855F7;

  /* Borders */
  --border-subtle: #3A3A42;
  --border-medium: #4A4A54;

  /* Shadows */
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 20px 50px rgba(0, 0, 0, 0.5);
  --shadow-coral: 0 8px 25px rgba(255, 107, 74, 0.35);

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
  --transition-smooth: 0.3s cubic-bezier(0.4, 0, 0.2, 1);

  /* Border Radius */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;
}

/* --------------------------------------------------------------------------
   2. Base Styles
   -------------------------------------------------------------------------- */
body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.6;
  color: var(--text-secondary);
  background-color: var(--bg-primary);
}

h1, h2, h3, h4, h5, h6 {
  color: var(--text-primary);
  font-weight: 700;
}

a {
  color: var(--coral);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--coral-hover);
}

::selection {
  background-color: var(--coral);
  color: var(--text-inverse);
}

/* --------------------------------------------------------------------------
   3. Bootstrap Overrides
   -------------------------------------------------------------------------- */

/* Navbar */
.navbar {
  background-color: var(--bg-secondary) !important;
  border-bottom: 1px solid var(--border-subtle) !important;
  padding: 0.75rem 0;
}

.navbar-brand {
  font-weight: 700;
  color: var(--text-primary) !important;
}

.navbar-nav .nav-link {
  color: var(--text-secondary) !important;
  font-weight: 500;
  padding: 0.5rem 1rem !important;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.navbar-nav .nav-link:hover {
  color: var(--coral) !important;
  background-color: var(--coral-glow);
}

.navbar-toggler {
  border-color: var(--border-subtle);
  padding: 0.5rem;
}

.navbar-toggler-icon {
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 30 30'%3e%3cpath stroke='rgba(255, 107, 74, 1)' stroke-linecap='round' stroke-miterlimit='10' stroke-width='2' d='M4 7h22M4 15h22M4 23h22'/%3e%3c/svg%3e");
}

.dropdown-menu {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-md);
  padding: 0.5rem;
}

.dropdown-item {
  color: var(--text-secondary);
  border-radius: var(--radius-sm);
  padding: 0.5rem 1rem;
  transition: all var(--transition-fast);
}

.dropdown-item:hover, .dropdown-item:focus {
  background-color: var(--coral-glow);
  color: var(--coral);
}

.dropdown-divider {
  border-color: var(--border-subtle);
}

/* Cards */
.card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-smooth);
}

.card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.card-body {
  padding: 1.5rem;
}

.card-title {
  color: var(--text-primary);
  font-weight: 600;
}

.card-text {
  color: var(--text-secondary);
}

/* Buttons - Primary (Coral) */
.btn-primary, .btn-coral {
  background: linear-gradient(135deg, var(--coral) 0%, #FF5733 100%);
  border: none;
  border-radius: var(--radius-md);
  color: var(--text-inverse);
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  transition: all var(--transition-smooth);
}

.btn-primary:hover, .btn-coral:hover {
  background: linear-gradient(135deg, var(--coral-hover) 0%, var(--coral) 100%);
  box-shadow: var(--shadow-coral);
  transform: translateY(-2px);
  color: var(--text-inverse);
}

.btn-primary:active, .btn-coral:active {
  transform: translateY(0) scale(0.98);
  box-shadow: 0 4px 15px rgba(255, 107, 74, 0.25);
}

.btn-primary:focus, .btn-coral:focus {
  box-shadow: 0 0 0 4px var(--coral-glow);
}

/* Buttons - Outline */
.btn-outline-primary, .btn-coral-outline {
  background: transparent;
  border: 2px solid var(--coral);
  border-radius: var(--radius-md);
  color: var(--coral);
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  transition: all var(--transition-smooth);
}

.btn-outline-primary:hover, .btn-coral-outline:hover {
  background: var(--coral-glow);
  border-color: var(--coral-hover);
  color: var(--coral-hover);
}

/* Buttons - Success */
.btn-success {
  background: linear-gradient(135deg, var(--success) 0%, #22C55E 100%);
  border: none;
  border-radius: var(--radius-md);
  color: var(--text-inverse);
  font-weight: 600;
}

.btn-success:hover {
  background: linear-gradient(135deg, #5EE898 0%, var(--success) 100%);
  box-shadow: 0 8px 25px rgba(74, 222, 128, 0.35);
  transform: translateY(-2px);
}

/* Buttons - Danger */
.btn-danger {
  background: linear-gradient(135deg, var(--error) 0%, #EF4444 100%);
  border: none;
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-weight: 600;
}

.btn-danger:hover {
  background: linear-gradient(135deg, #FCA5A5 0%, var(--error) 100%);
  box-shadow: 0 8px 25px rgba(248, 113, 113, 0.35);
  transform: translateY(-2px);
}

/* Buttons - Secondary/Outline Secondary */
.btn-secondary, .btn-outline-secondary {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  font-weight: 500;
}

.btn-secondary:hover, .btn-outline-secondary:hover {
  background: var(--bg-elevated);
  border-color: var(--border-medium);
  color: var(--text-primary);
}

/* Forms */
.form-control, .form-select {
  background-color: var(--bg-tertiary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  padding: 0.75rem 1rem;
  transition: all var(--transition-fast);
}

.form-control::placeholder {
  color: var(--text-muted);
}

.form-control:focus, .form-select:focus {
  background-color: var(--bg-elevated);
  border-color: var(--coral);
  box-shadow: 0 0 0 4px var(--coral-glow);
  color: var(--text-primary);
}

.form-label {
  color: var(--text-secondary);
  font-weight: 500;
  margin-bottom: 0.5rem;
}

.form-select {
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3e%3cpath fill='none' stroke='%23FF6B4A' stroke-linecap='round' stroke-linejoin='round' stroke-width='2' d='m2 5 6 6 6-6'/%3e%3c/svg%3e");
}

.form-check-input {
  background-color: var(--bg-tertiary);
  border-color: var(--border-medium);
}

.form-check-input:checked {
  background-color: var(--coral);
  border-color: var(--coral);
}

.form-check-input:focus {
  box-shadow: 0 0 0 4px var(--coral-glow);
  border-color: var(--coral);
}

.form-check-label {
  color: var(--text-secondary);
}

.input-group-text {
  background-color: var(--bg-tertiary);
  border: 1px solid var(--border-subtle);
  color: var(--text-muted);
}

/* Alerts */
.alert {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-left: 4px solid;
  border-radius: var(--radius-md);
  color: var(--text-secondary);
}

.alert-success {
  border-left-color: var(--success);
  background-color: var(--success-bg);
}

.alert-danger {
  border-left-color: var(--error);
  background-color: var(--error-bg);
}

.alert-warning {
  border-left-color: var(--warning);
  background-color: var(--warning-bg);
}

.alert-info {
  border-left-color: var(--info);
  background-color: var(--info-bg);
}

.alert-primary {
  border-left-color: var(--coral);
  background-color: rgba(255, 107, 74, 0.1);
}

.alert .btn-close {
  filter: invert(1) grayscale(100%) brightness(200%);
}

/* Badges */
.badge {
  border-radius: var(--radius-full);
  font-weight: 600;
  padding: 0.4rem 0.8rem;
}

.badge.bg-primary {
  background: linear-gradient(135deg, var(--coral) 0%, #FF5733 100%) !important;
}

.badge.bg-success {
  background: var(--success-glow) !important;
  color: var(--success) !important;
}

.badge.bg-danger {
  background: var(--error-glow) !important;
  color: var(--error) !important;
}

.badge.bg-warning {
  background: var(--warning-glow) !important;
  color: var(--warning) !important;
}

.badge.bg-info {
  background: var(--info-glow) !important;
  color: var(--info) !important;
}

.badge.bg-secondary {
  background: var(--bg-tertiary) !important;
  color: var(--text-secondary) !important;
}

/* Progress Bars */
.progress {
  background-color: var(--bg-tertiary);
  border-radius: var(--radius-full);
  height: 10px;
  overflow: hidden;
}

.progress-bar {
  background: linear-gradient(90deg, var(--coral) 0%, var(--coral-hover) 100%);
  border-radius: var(--radius-full);
  position: relative;
  overflow: hidden;
}

.progress-bar::after {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.3), transparent);
  animation: shimmer 2s infinite;
}

.progress-bar-striped {
  background-image: linear-gradient(45deg, rgba(255,255,255,.15) 25%, transparent 25%, transparent 50%, rgba(255,255,255,.15) 50%, rgba(255,255,255,.15) 75%, transparent 75%, transparent);
}

/* Tables */
.table {
  color: var(--text-secondary);
}

.table thead th {
  background-color: var(--bg-tertiary);
  color: var(--text-primary);
  border-bottom-color: var(--border-subtle);
  font-weight: 600;
}

.table tbody td {
  border-color: var(--border-subtle);
}

.table-striped tbody tr:nth-of-type(odd) {
  background-color: rgba(255, 255, 255, 0.02);
}

.table-hover tbody tr:hover {
  background-color: var(--coral-glow);
}

/* --------------------------------------------------------------------------
   4. Custom Components
   -------------------------------------------------------------------------- */

/* Course Cards */
.course-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: all var(--transition-smooth);
}

.course-card:hover {
  transform: translateY(-4px);
  border-left: 3px solid var(--coral);
  box-shadow: var(--shadow-lg);
}

.course-card .card-img-top {
  border-radius: 0;
  aspect-ratio: 16/9;
  object-fit: cover;
}

/* Flashcard Container */
.flashcard-container {
  background: linear-gradient(145deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: 2.5rem;
  box-shadow: var(--shadow-lg);
  max-width: 600px;
  margin: 0 auto;
}

.flashcard-container .target-text {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--text-primary);
  text-align: center;
  margin-bottom: 2rem;
}

.flashcard-input {
  background: var(--bg-tertiary);
  border: 2px solid var(--border-subtle);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 1.25rem;
  padding: 1rem 1.5rem;
  width: 100%;
  text-align: center;
  transition: all var(--transition-fast);
}

.flashcard-input:focus {
  border-color: var(--coral);
  box-shadow: 0 0 0 4px var(--coral-glow);
  outline: none;
}

/* Character Keyboard Buttons */
.char-btn {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-full);
  color: var(--text-secondary);
  font-size: 1rem;
  font-weight: 600;
  padding: 0.5rem 1rem;
  margin: 0.25rem;
  transition: all var(--transition-fast);
  cursor: pointer;
}

.char-btn:hover {
  background: var(--coral-glow);
  border-color: var(--coral);
  color: var(--coral);
}

/* Status Badges */
.badge-processing {
  background: var(--warning-glow) !important;
  color: var(--warning) !important;
  animation: pulse 2s infinite;
}

.badge-ready {
  background: var(--success-glow) !important;
  color: var(--success) !important;
}

.badge-error {
  background: var(--error-glow) !important;
  color: var(--error) !important;
}

/* Feedback States */
.feedback-correct {
  background: linear-gradient(135deg, var(--success-bg) 0%, #0D3D28 100%);
  animation: celebratePulse 0.5s ease-out;
}

.feedback-incorrect {
  background: linear-gradient(135deg, var(--error-bg) 0%, #4A1717 100%);
  animation: gentleShake 0.5s ease-out;
}

/* Hero Section */
.hero-section {
  padding: 4rem 0;
  text-align: center;
}

.hero-title {
  font-size: 3rem;
  font-weight: 800;
  color: var(--text-primary);
  line-height: 1.1;
  margin-bottom: 1.5rem;
}

.hero-title .accent {
  background: linear-gradient(135deg, var(--coral) 0%, var(--coral-hover) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 2rem;
}

/* Feature Cards */
.feature-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 2rem;
  text-align: center;
  transition: all var(--transition-smooth);
}

.feature-card:hover {
  border-color: var(--coral);
  transform: translateY(-4px);
}

.feature-icon {
  width: 64px;
  height: 64px;
  background: var(--coral-glow);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1.5rem;
  font-size: 1.5rem;
  color: var(--coral);
}

/* Step Numbers */
.step-number {
  width: 48px;
  height: 48px;
  min-width: 48px;
  background: linear-gradient(135deg, var(--coral) 0%, #FF5733 100%);
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-inverse);
  box-shadow: 0 4px 15px rgba(255, 107, 74, 0.3);
}

/* Premium Badge */
.badge-premium {
  background: linear-gradient(135deg, var(--xp-gold) 0%, #FFA500 100%);
  color: var(--text-inverse);
  font-weight: 700;
  box-shadow: 0 2px 10px rgba(255, 215, 0, 0.3);
}

/* XP Badge */
.xp-badge {
  background: linear-gradient(135deg, var(--xp-gold) 0%, #FFA500 100%);
  color: var(--text-inverse);
  border-radius: var(--radius-full);
  padding: 0.25rem 0.75rem;
  font-weight: 700;
  font-size: 0.875rem;
}

/* Streak Counter */
.streak-counter {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--streak-orange);
  font-weight: 600;
}

.streak-flame {
  font-size: 1.25rem;
}

/* Progress Ring (SVG) */
.progress-ring {
  transform: rotate(-90deg);
}

.progress-ring circle {
  fill: none;
  stroke-width: 4;
}

.progress-ring .progress-ring-bg {
  stroke: var(--bg-tertiary);
}

.progress-ring .progress-ring-fill {
  stroke: var(--coral);
  stroke-linecap: round;
  transition: stroke-dashoffset 0.5s ease;
}

/* Video Container */
.video-container {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.video-container video {
  width: 100%;
  display: block;
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: 4rem 2rem;
}

.empty-state-icon {
  font-size: 4rem;
  color: var(--coral);
  margin-bottom: 1.5rem;
}

.empty-state-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.75rem;
}

.empty-state-text {
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
}

/* --------------------------------------------------------------------------
   5. Utilities
   -------------------------------------------------------------------------- */

/* Text Colors */
.text-coral { color: var(--coral) !important; }
.text-coral-hover:hover { color: var(--coral-hover) !important; }
.text-light-primary { color: var(--text-primary) !important; }
.text-light-secondary { color: var(--text-secondary) !important; }
.text-light-muted { color: var(--text-muted) !important; }

/* Background Colors */
.bg-dark-primary { background-color: var(--bg-primary) !important; }
.bg-dark-secondary { background-color: var(--bg-secondary) !important; }
.bg-dark-tertiary { background-color: var(--bg-tertiary) !important; }

/* Border Utilities */
.border-coral { border-color: var(--coral) !important; }
.border-subtle { border-color: var(--border-subtle) !important; }
.border-left-coral { border-left: 3px solid var(--coral) !important; }

/* Shadow Utilities */
.shadow-dark-sm { box-shadow: var(--shadow-sm) !important; }
.shadow-dark-md { box-shadow: var(--shadow-md) !important; }
.shadow-dark-lg { box-shadow: var(--shadow-lg) !important; }
.shadow-coral-glow { box-shadow: var(--shadow-coral) !important; }

/* --------------------------------------------------------------------------
   6. Animations & Keyframes
   -------------------------------------------------------------------------- */

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

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

@keyframes slideInRight {
  from { opacity: 0; transform: translateX(20px); }
  to { opacity: 1; transform: translateX(0); }
}

@keyframes bounce {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

@keyframes gentleShake {
  0%, 100% { transform: translateX(0); }
  20%, 60% { transform: translateX(-5px); }
  40%, 80% { transform: translateX(5px); }
}

@keyframes celebratePulse {
  0% { transform: scale(0.95); opacity: 0; }
  50% { transform: scale(1.02); }
  100% { transform: scale(1); opacity: 1; }
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.7; }
}

@keyframes shimmer {
  0% { left: -100%; }
  100% { left: 100%; }
}

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

/* Animation Utilities */
.animate-fade-in { animation: fadeIn 0.3s ease-out; }
.animate-slide-up { animation: slideUp 0.3s ease-out; }
.animate-bounce { animation: bounce 0.5s ease; }
.animate-pulse { animation: pulse 2s infinite; }
.animate-shake { animation: gentleShake 0.5s ease; }

/* --------------------------------------------------------------------------
   7. Responsive Adjustments
   -------------------------------------------------------------------------- */

@media (max-width: 768px) {
  .hero-title {
    font-size: 2rem;
  }

  .flashcard-container {
    padding: 1.5rem;
    margin: 0 1rem;
  }

  .flashcard-container .target-text {
    font-size: 1.25rem;
  }

  .flashcard-input {
    font-size: 1rem;
    padding: 0.75rem 1rem;
  }
}

@media (min-width: 992px) {
  .hero-section {
    padding: 6rem 0;
  }
}

/* --------------------------------------------------------------------------
   8. Legacy Support (for gradual migration)
   -------------------------------------------------------------------------- */

/* Old brand color references */
.brand-color {
  color: var(--coral);
}

.brand-bg {
  background-color: var(--coral);
}

/* Old loading spinner */
.loading-spinner {
  color: var(--coral);
}

/* Old section styling */
.section-light {
  background-color: var(--bg-secondary);
}

/* Content section spacing */
.content-section {
  margin-top: 2rem;
  margin-bottom: 2rem;
}

@media (min-width: 768px) {
  .content-section {
    margin-top: 3rem;
    margin-bottom: 3rem;
  }
}

/* Footer */
.footer {
  font-size: 0.875rem;
  color: var(--text-muted);
}