/* ===============================================
   Smart To-Do App - Professional Styles
   ===============================================
   Modern, responsive design showcasing advanced
   CSS techniques and clean architecture
   =============================================== */

/* CSS Custom Properties */
:root {
  /* Primary Color Palette */
  --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  --success-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
  --warning-gradient: linear-gradient(135deg, #fad961 0%, #f76b1c 100%);
  
  /* Glass Morphism - Light Mode */
  --glass-bg: rgba(255, 255, 255, 0.25);
  --glass-bg-strong: rgba(255, 255, 255, 0.35);
  --glass-border: rgba(255, 255, 255, 0.18);
  --glass-shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.37);
  
  /* Colors - Light Mode */
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --text-accent: #667eea;
  --bg-primary: #ffffff;
  --bg-secondary: #f9fafb;
  --border-color: rgba(209, 213, 219, 0.3);
  
  /* Typography */
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-weight-light: 300;
  --font-weight-regular: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;
  --font-weight-extrabold: 800;
  
  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  
  /* Border Radius */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  --radius-2xl: 24px;
  --radius-full: 50px;
  
  /* 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);
  
  /* Animations */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
}

/* Dark Mode Theme */
[data-theme="dark"] {
  /* Glass Morphism - Dark Mode */
  --glass-bg: rgba(20, 24, 35, 0.4);
  --glass-bg-strong: rgba(20, 24, 35, 0.6);
  --glass-border: rgba(255, 255, 255, 0.1);
  --glass-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.6);
  
  /* Colors - Dark Mode */
  --text-primary: #f9fafb;
  --text-secondary: #d1d5db;
  --text-accent: #818cf8;
  --bg-primary: #111827;
  --bg-secondary: #1f2937;
  --border-color: rgba(255, 255, 255, 0.1);
}

/* Reset & Base Styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  font-size: 16px;
  line-height: 1.5;
}

body {
  font-family: var(--font-family);
  background: var(--primary-gradient);
  background-attachment: fixed;
  min-height: 100vh;
  color: #1f2937;
  overflow-x: hidden;
  position: relative;
}

/* Background Elements */
.background-elements {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 0;
}

.floating-shape {
  position: absolute;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 50%;
  animation: float 20s infinite linear;
}

.shape-1 {
  width: 300px;
  height: 300px;
  top: 10%;
  left: -150px;
  animation-delay: 0s;
}

.shape-2 {
  width: 200px;
  height: 200px;
  top: 60%;
  right: -100px;
  animation-delay: -10s;
}

.shape-3 {
  width: 150px;
  height: 150px;
  top: 80%;
  left: 20%;
  animation-delay: -5s;
}

@keyframes float {
  0%, 100% { transform: translateY(0px) rotate(0deg); }
  25% { transform: translateY(-20px) rotate(90deg); }
  50% { transform: translateY(0px) rotate(180deg); }
  75% { transform: translateY(-10px) rotate(270deg); }
}

/* Main App Container */
.app-container {
  position: relative;
  z-index: 1;
  max-width: 900px;
  margin: 0 auto;
  padding: var(--spacing-lg);
  min-height: 100vh;
}

/* Header Section */
.app-header {
  background: var(--glass-bg-strong);
  backdrop-filter: blur(20px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-2xl);
  box-shadow: var(--glass-shadow);
  padding: var(--spacing-2xl);
  margin-bottom: var(--spacing-xl);
  animation: slideInDown 0.8s ease-out;
}

.header-content {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: var(--spacing-xl);
  align-items: center;
}

.logo-section {
  text-align: left;
}

.logo-icon {
  display: inline-block;
  width: 60px;
  height: 60px;
  background: var(--primary-gradient);
  border-radius: var(--radius-md);
  color: white;
  font-size: 28px;
  font-weight: var(--font-weight-bold);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--spacing-md);
  box-shadow: var(--shadow-md);
}

.app-title {
  font-size: 2.5rem;
  font-weight: var(--font-weight-extrabold);
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: var(--spacing-xs);
}

.app-subtitle {
  font-size: 1.1rem;
  color: #6b7280;
  font-weight: var(--font-weight-medium);
}

.stats-dashboard {
  display: flex;
  gap: var(--spacing-md);
}

.stat-card {
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  min-width: 100px;
  text-align: center;
  transition: var(--transition-normal);
}

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

.stat-icon {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-sm);
}

.stat-number {
  display: block;
  font-size: 1.8rem;
  font-weight: var(--font-weight-bold);
  color: #1f2937;
}

.stat-label {
  font-size: 0.8rem;
  color: #6b7280;
  font-weight: var(--font-weight-medium);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

/* Theme Toggle Button */
.theme-toggle {
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-full);
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition-normal);
  backdrop-filter: blur(10px);
  margin-left: var(--spacing-md);
}

.theme-toggle:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  background: var(--glass-bg-strong);
}

.theme-icon {
  font-size: 1.5rem;
  transition: var(--transition-normal);
}

[data-theme="dark"] .theme-icon {
  transform: rotate(180deg);
}

/* Input Section */
.input-section {
  background: var(--glass-bg-strong);
  backdrop-filter: blur(20px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-2xl);
  box-shadow: var(--glass-shadow);
  padding: var(--spacing-2xl);
  margin-bottom: var(--spacing-xl);
  animation: slideInLeft 0.8s ease-out 0.2s both;
}

.input-container {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.input-group {
  position: relative;
  display: flex;
  align-items: center;
  background: rgba(255, 255, 255, 0.8);
  border: 2px solid transparent;
  border-radius: var(--radius-full);
  padding: var(--spacing-sm);
  transition: var(--transition-normal);
}

.input-group:focus-within {
  border-color: #667eea;
  box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
  background: rgba(255, 255, 255, 0.95);
}

.input-icon {
  font-size: 1.2rem;
  margin: 0 var(--spacing-md);
  color: #6b7280;
}

.task-input {
  flex: 1;
  border: none;
  outline: none;
  background: transparent;
  font-size: 1.1rem;
  padding: var(--spacing-md);
  color: #1f2937;
  font-weight: var(--font-weight-medium);
}

.task-input::placeholder {
  color: #9ca3af;
  font-weight: var(--font-weight-regular);
}

.input-counter {
  font-size: 0.8rem;
  color: #6b7280;
  margin-right: var(--spacing-md);
  font-weight: var(--font-weight-medium);
}

.input-controls {
  display: flex;
  gap: var(--spacing-lg);
  align-items: center;
}

.priority-selector {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xs);
}

.priority-label {
  font-size: 0.8rem;
  font-weight: var(--font-weight-semibold);
  color: #374151;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.priority-select {
  background: rgba(255, 255, 255, 0.8);
  border: 1px solid rgba(209, 213, 219, 0.5);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  font-size: 0.9rem;
  font-weight: var(--font-weight-medium);
  cursor: pointer;
  transition: var(--transition-normal);
}

.priority-select:focus {
  outline: none;
  border-color: #667eea;
  box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.add-task-btn {
  background: var(--primary-gradient);
  color: white;
  border: none;
  border-radius: var(--radius-full);
  padding: var(--spacing-lg) var(--spacing-2xl);
  font-size: 1rem;
  font-weight: var(--font-weight-semibold);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  transition: var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.add-task-btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
  transition: var(--transition-slow);
}

.add-task-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-xl);
}

.add-task-btn:hover::before {
  left: 100%;
}

.btn-icon {
  font-size: 1.2rem;
  font-weight: var(--font-weight-bold);
}

/* Filters Section */
.filters-section {
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  padding: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
  animation: slideInRight 0.8s ease-out 0.4s both;
}

.filter-container {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.filter-label {
  font-size: 0.9rem;
  font-weight: var(--font-weight-semibold);
  color: #374151;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.filter-buttons {
  display: flex;
  gap: var(--spacing-sm);
  flex-wrap: wrap;
}

.filter-btn {
  background: rgba(255, 255, 255, 0.6);
  border: 1px solid rgba(209, 213, 219, 0.3);
  border-radius: var(--radius-full);
  padding: var(--spacing-sm) var(--spacing-lg);
  font-size: 0.9rem;
  font-weight: var(--font-weight-medium);
  cursor: pointer;
  transition: var(--transition-normal);
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.filter-btn:hover {
  background: rgba(255, 255, 255, 0.8);
  transform: translateY(-1px);
}

.filter-btn.active {
  background: var(--primary-gradient);
  color: white;
  border-color: transparent;
  box-shadow: var(--shadow-md);
}

.filter-icon {
  font-size: 1rem;
}

/* Tasks Section */
.tasks-section {
  background: var(--glass-bg-strong);
  backdrop-filter: blur(20px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-2xl);
  box-shadow: var(--glass-shadow);
  padding: var(--spacing-2xl);
  margin-bottom: var(--spacing-xl);
  animation: slideInUp 0.8s ease-out 0.6s both;
}

.tasks-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--spacing-xl);
  padding-bottom: var(--spacing-lg);
  border-bottom: 1px solid rgba(209, 213, 219, 0.3);
}

.tasks-title {
  font-size: 1.5rem;
  font-weight: var(--font-weight-bold);
  color: #1f2937;
}

.clear-btn {
  background: var(--secondary-gradient);
  color: white;
  border: none;
  border-radius: var(--radius-md);
  padding: var(--spacing-sm) var(--spacing-md);
  cursor: pointer;
  transition: var(--transition-normal);
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.clear-btn:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

/* Task List */
.task-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  max-height: 600px;
  overflow-y: auto;
}

.task-item {
  background: rgba(255, 255, 255, 0.8);
  border: 1px solid rgba(209, 213, 219, 0.3);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  transition: var(--transition-normal);
  animation: taskSlideIn 0.4s ease-out;
}

.task-item:hover {
  background: rgba(255, 255, 255, 0.95);
  transform: translateX(4px);
  box-shadow: var(--shadow-md);
}

.task-item.completed {
  opacity: 0.7;
  background: rgba(34, 197, 94, 0.1);
  border-color: rgba(34, 197, 94, 0.3);
}

.task-checkbox {
  width: 20px;
  height: 20px;
  border: 2px solid #d1d5db;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition-normal);
  position: relative;
}

.task-checkbox.checked {
  background: var(--success-gradient);
  border-color: transparent;
  color: white;
}

.priority-indicator {
  width: 4px;
  height: 40px;
  border-radius: var(--radius-sm);
  margin-right: var(--spacing-sm);
}

.priority-high { background: #ef4444; }
.priority-medium { background: #f59e0b; }
.priority-low { background: #10b981; }

.task-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xs);
}

.task-text {
  font-size: 1rem;
  font-weight: var(--font-weight-medium);
  color: #1f2937;
  line-height: 1.4;
  word-break: break-word;
}

.task-item.completed .task-text {
  text-decoration: line-through;
  color: #6b7280;
}

.task-meta {
  font-size: 0.8rem;
  color: #6b7280;
  display: flex;
  gap: var(--spacing-md);
  align-items: center;
}

.task-actions {
  display: flex;
  gap: var(--spacing-sm);
}

.action-btn {
  background: transparent;
  border: none;
  border-radius: var(--radius-sm);
  padding: var(--spacing-sm);
  cursor: pointer;
  font-size: 1.1rem;
  transition: var(--transition-normal);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
}

.action-btn:hover {
  background: rgba(0, 0, 0, 0.05);
  transform: scale(1.1);
}

.complete-btn { color: #10b981; }
.edit-btn { color: #3b82f6; }
.delete-btn { color: #ef4444; }

/* Empty State */
.empty-state {
  text-align: center;
  padding: var(--spacing-2xl);
  color: #6b7280;
}

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

.empty-title {
  font-size: 1.5rem;
  font-weight: var(--font-weight-semibold);
  color: #374151;
  margin-bottom: var(--spacing-md);
}

.empty-description {
  font-size: 1rem;
  max-width: 400px;
  margin: 0 auto;
}

/* Tools Section */
.tools-section {
  background: var(--glass-bg);
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  padding: var(--spacing-lg);
  animation: fadeIn 0.8s ease-out 0.8s both;
}

.tools-header {
  margin-bottom: var(--spacing-lg);
}

.tools-title {
  font-size: 1.2rem;
  font-weight: var(--font-weight-semibold);
  color: #374151;
}

.tools-buttons {
  display: flex;
  gap: var(--spacing-md);
  flex-wrap: wrap;
}

.tool-btn {
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  padding: var(--spacing-md) var(--spacing-lg);
  cursor: pointer;
  transition: var(--transition-normal);
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-weight: var(--font-weight-medium);
}

.tool-btn:hover {
  background: rgba(255, 255, 255, 0.8);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.export-btn { color: #059669; }
.import-btn { color: #dc2626; }

.tool-icon {
  font-size: 1.1rem;
}

/* Notifications */
.notification-container {
  position: fixed;
  top: var(--spacing-lg);
  right: var(--spacing-lg);
  z-index: 1000;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.notification {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg);
  box-shadow: var(--shadow-lg);
  min-width: 300px;
  animation: notificationSlide 0.3s ease-out;
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.notification.success { border-left: 4px solid #10b981; }
.notification.warning { border-left: 4px solid #f59e0b; }
.notification.error { border-left: 4px solid #ef4444; }
.notification.info { border-left: 4px solid #3b82f6; }

/* Loading Overlay */
.loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.5);
  backdrop-filter: blur(5px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 2000;
}

.loading-spinner {
  width: 50px;
  height: 50px;
  border: 4px solid rgba(255, 255, 255, 0.3);
  border-radius: 50%;
  border-top-color: white;
  animation: spin 1s ease-in-out infinite;
  margin-bottom: var(--spacing-lg);
}

.loading-text {
  color: white;
  font-size: 1.1rem;
  font-weight: var(--font-weight-medium);
}

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

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

@keyframes slideInLeft {
  from {
    opacity: 0;
    transform: translateX(-30px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

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

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

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

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

@keyframes notificationSlide {
  from {
    opacity: 0;
    transform: translateX(100%);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

/* Utility Classes */
.hidden { display: none !important; }

/* Responsive Design */
@media (max-width: 768px) {
  .app-container {
    padding: var(--spacing-md);
  }
  
  .header-content {
    grid-template-columns: 1fr;
    text-align: center;
    gap: var(--spacing-lg);
  }
  
  .stats-dashboard {
    justify-content: center;
  }
  
  .app-title {
    font-size: 2rem;
  }
  
  .input-controls {
    flex-direction: column;
    align-items: stretch;
  }
  
  .add-task-btn {
    width: 100%;
    justify-content: center;
  }
  
  .filter-buttons {
    justify-content: center;
  }
  
  .tools-buttons {
    justify-content: center;
  }
  
  .notification-container {
    left: var(--spacing-md);
    right: var(--spacing-md);
  }
  
  .notification {
    min-width: auto;
  }
}

@media (max-width: 480px) {
  .app-container {
    padding: var(--spacing-sm);
  }
  
  .app-header,
  .input-section,
  .tasks-section {
    padding: var(--spacing-lg);
  }
  
  .stats-dashboard {
    flex-direction: column;
    gap: var(--spacing-sm);
  }
  
  .stat-card {
    min-width: auto;
  }
  
  .task-item {
    padding: var(--spacing-md);
  }
  
  .task-actions {
    flex-direction: column;
  }
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  .glass-card,
  .stat-card,
  .task-item {
    border: 2px solid #000;
    background: rgba(255, 255, 255, 0.95);
  }
  
  .filter-btn.active {
    border: 2px solid #000;
  }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  
  .floating-shape {
    animation: none;
  }
}

/* Focus indicators for accessibility */
.task-input:focus,
.priority-select:focus,
.add-task-btn:focus,
.filter-btn:focus,
.action-btn:focus,
.tool-btn:focus {
  outline: 2px solid #667eea;
  outline-offset: 2px;
}

/* Print styles */
@media print {
  .background-elements,
  .tools-section,
  .notification-container,
  .loading-overlay {
    display: none;
  }
  
  .app-container {
    background: white;
    box-shadow: none;
  }
  
  .glass-card {
    background: white;
    border: 1px solid #ccc;
  }
}