/* Modern CSS Variables */
:root {
  --primary-color: #6366f1;
  --primary-hover: #4f46e5;
  --secondary-color: #ec4899;
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --bg-primary: #f9fafb;
  --bg-secondary: #ffffff;
  --border-color: #e5e7eb;
  --success-color: #10b981;
  --warning-color: #f59e0b;
  --danger-color: #ef4444;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Dark mode variables */
.dark {
  --text-primary: #f9fafb;
  --text-secondary: #9ca3af;
  --bg-primary: #111827;
  --bg-secondary: #1f2937;
  --border-color: #374151;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  transition: var(--transition);
  line-height: 1.6;
}

/* App container */
.app-container {
  max-width: 800px;
  margin: 0 auto;
  padding: 1.5rem;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header */
.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border-color);
}

.app-title {
  font-size: 1.75rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.theme-toggle {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  padding: 0.5rem;
  border-radius: 0.5rem;
  transition: var(--transition);
}

.theme-toggle:hover {
  background: var(--bg-secondary);
}

/* Main content */
.app-main {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 2rem;
}

/* Topic section */
.topic-section {
  background: var(--bg-secondary);
  border-radius: 1rem;
  padding: 2rem;
  box-shadow: var(--shadow-md);
  text-align: center;
  transition: var(--transition);
}

.category-badge {
  display: inline-block;
  background: var(--primary-color);
  color: white;
  padding: 0.5rem 1rem;
  border-radius: 1.5rem;
  font-size: 0.875rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.topic-display {
  margin: 2rem 0;
  min-height: 150px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.topic-text {
  font-size: 1.5rem;
  font-weight: 600;
  line-height: 1.4;
  color: var(--text-primary);
  transition: var(--transition);
}

/* Buttons */
.generate-btn, .regenerate-btn {
  background: var(--primary-color);
  color: white;
  border: none;
  padding: 1rem 2rem;
  border-radius: 0.75rem;
  font-size: 1.125rem;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  transition: var(--transition);
  box-shadow: var(--shadow-md);
}

.generate-btn:hover, .regenerate-btn:hover {
  background: var(--primary-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.generate-btn:active, .regenerate-btn:active {
  transform: translateY(0);
}

.btn-icon {
  font-size: 1.25rem;
}

/* Timer section */
.timer-section {
  background: var(--bg-secondary);
  border-radius: 1rem;
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
}

.timer-controls {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.5rem;
}

.duration-selector {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  justify-content: center;
}

.duration-btn {
  padding: 0.5rem 1rem;
  border: 2px solid var(--border-color);
  background: var(--bg-primary);
  color: var(--text-secondary);
  border-radius: 0.5rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.duration-btn:hover {
  border-color: var(--primary-color);
  color: var(--primary-color);
}

.duration-btn.active {
  background: var(--primary-color);
  border-color: var(--primary-color);
  color: white;
}

.timer-display {
  font-size: 4rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: var(--text-primary);
}

.timer-controls-buttons {
  display: flex;
  gap: 1rem;
}

.timer-btn {
  width: 4rem;
  height: 4rem;
  border-radius: 50%;
  border: none;
  background: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 1.5rem;
  cursor: pointer;
  box-shadow: var(--shadow-md);
  transition: var(--transition);
  display: flex;
  align-items: center;
  justify-content: center;
}

.timer-btn:hover:not(:disabled) {
  background: var(--primary-color);
  color: white;
  transform: scale(1.05);
}

.timer-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* Filters section */
.filters-section {
  background: var(--bg-secondary);
  border-radius: 1rem;
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
}

.category-filters {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  justify-content: center;
}

.filter-btn {
  padding: 0.5rem 1rem;
  border: 1px solid var(--border-color);
  background: var(--bg-primary);
  color: var(--text-secondary);
  border-radius: 1.5rem;
  font-size: 0.875rem;
  cursor: pointer;
  transition: var(--transition);
}

.filter-btn:hover {
  border-color: var(--primary-color);
  color: var(--primary-color);
}

.filter-btn.active {
  background: var(--primary-color);
  border-color: var(--primary-color);
  color: white;
}

/* Favorites section */
.favorites-section {
  background: var(--bg-secondary);
  border-radius: 1rem;
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
}

.favorites-title {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: 1rem;
  color: var(--text-primary);
}

.favorites-list {
  min-height: 100px;
}

.favorites-empty {
  color: var(--text-secondary);
  font-style: italic;
  text-align: center;
}

.favorites-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem;
  background: var(--bg-primary);
  border-radius: 0.5rem;
  margin-bottom: 0.5rem;
  transition: var(--transition);
}

.favorites-item:hover {
  background: var(--border-color);
}

.favorites-text {
  flex: 1;
  font-size: 0.9375rem;
  color: var(--text-primary);
}

.favorites-actions {
  display: flex;
  gap: 0.5rem;
}

.favorites-btn {
  background: none;
  border: none;
  font-size: 1rem;
  cursor: pointer;
  padding: 0.25rem 0.5rem;
  border-radius: 0.25rem;
  transition: var(--transition);
}

.favorites-btn:hover {
  background: var(--border-color);
}

/* Featured section */
.featured-section {
  background: var(--bg-secondary);
  border-radius: 1rem;
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
}

.featured-topic {
  text-align: center;
}

.featured-badge {
  display: inline-block;
  background: var(--secondary-color);
  color: white;
  padding: 0.25rem 0.75rem;
  border-radius: 1rem;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 1rem;
}

.featured-text {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.4;
}

/* Footer */
.app-footer {
  margin-top: 2rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.kofi-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: #29abca;
  color: white;
  padding: 0.75rem 1.5rem;
  border-radius: 1.5rem;
  font-weight: 600;
  text-decoration: none;
  transition: var(--transition);
  box-shadow: var(--shadow-md);
}

.kofi-btn:hover {
  background: #2496b0;
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.kofi-icon {
  font-size: 1.25rem;
}

.app-version {
  color: var(--text-secondary);
  font-size: 0.875rem;
}

/* Animations */
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

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

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

.topic-text.animate {
  animation: fadeIn 0.5s ease-out;
}

.generate-btn.animate {
  animation: pulse 0.5s ease-out;
}

/* Mobile responsiveness */
@media (max-width: 640px) {
  .app-container {
    padding: 1rem;
  }

  .app-title {
    font-size: 1.5rem;
  }

  .topic-text {
    font-size: 1.25rem;
  }

  .timer-display {
    font-size: 3rem;
  }

  .duration-selector {
    gap: 0.25rem;
  }

  .duration-btn {
    padding: 0.25rem 0.75rem;
    font-size: 0.875rem;
  }

  .favorites-list {
    max-height: 300px;
    overflow-y: auto;
  }
}

/* Print styles */
@media print {
  .theme-toggle, .timer-controls-buttons, .regenerate-btn, .kofi-btn {
    display: none;
  }

  .app-container {
    max-width: 100%;
    padding: 0;
  }

  .topic-section, .timer-section, .favorites-section, .featured-section {
    box-shadow: none;
  }
}