/* CSS Custom Properties for Theme Support */
:root {
  /* Light Theme Colors */
  --primary-color: #4f46e5;
  --primary-hover: #4338ca;
  --secondary-color: #6b7280;
  --success-color: #10b981;
  --warning-color: #f59e0b;
  --danger-color: #ef4444;

  /* Background Colors */
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #f1f5f9;
  --bg-modal: rgba(0, 0, 0, 0.5);

  /* Text Colors */
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --text-tertiary: #9ca3af;
  --text-inverse: #ffffff;

  /* Border Colors */
  --border-light: #e5e7eb;
  --border-medium: #d1d5db;
  --border-dark: #9ca3af;

  /* Shadow */
  --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);

  /* Category Colors */
  --category-personal: #ec4899;
  --category-work: #3b82f6;
  --category-shopping: #10b981;
  --category-health: #f59e0b;
  --category-education: #8b5cf6;

  /* Priority Colors */
  --priority-high: #ef4444;
  --priority-medium: #f59e0b;
  --priority-low: #10b981;

  /* Transitions */
  --transition-fast: 0.15s ease-in-out;
  --transition-normal: 0.3s ease-in-out;
  --transition-slow: 0.5s ease-in-out;
}

/* Dark Theme */
[data-theme="dark"] {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-tertiary: #334155;
  --bg-modal: rgba(0, 0, 0, 0.8);

  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-tertiary: #94a3b8;

  --border-light: #334155;
  --border-medium: #475569;
  --border-dark: #64748b;
}

/* 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-color: var(--bg-secondary);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background-color var(--transition-normal),
    color var(--transition-normal);
}

/* App Container */
.app-container {
  min-height: 100vh;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1rem;
}

/* Header */
.header {
  padding: 1.5rem 0;
  border-bottom: 1px solid var(--border-light);
  margin-bottom: 2rem;
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.app-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--primary-color);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.theme-toggle {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-medium);
  border-radius: 0.5rem;
  padding: 0.75rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  color: var(--text-secondary);
}

.theme-toggle:hover {
  background: var(--primary-color);
  color: var(--text-inverse);
  transform: translateY(-1px);
}

/* Main Content */
.main-content {
  display: grid;
  gap: 2rem;
}

/* Add Task Section */
.add-task-section {
  background: var(--bg-primary);
  border-radius: 1rem;
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
  border: 1px solid var(--border-light);
}

.add-task-form {
  display: grid;
  gap: 1rem;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 1rem;
  align-items: end;
}

.form-details {
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border-light);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.form-group label {
  font-weight: 500;
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.task-input {
  flex: 1;
  padding: 0.875rem 1rem;
  border: 2px solid var(--border-light);
  border-radius: 0.5rem;
  font-size: 1rem;
  background: var(--bg-primary);
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.task-input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.form-input,
.form-select {
  padding: 0.75rem;
  border: 1px solid var(--border-medium);
  border-radius: 0.5rem;
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: 0.875rem;
  transition: all var(--transition-fast);
}

.form-input:focus,
.form-select:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.add-btn {
  background: var(--primary-color);
  color: var(--text-inverse);
  border: none;
  border-radius: 0.5rem;
  padding: 0.875rem 1.5rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  white-space: nowrap;
}

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

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

.search-bar {
  position: relative;
  margin-bottom: 1.5rem;
}

.search-bar i {
  position: absolute;
  left: 1rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-tertiary);
}

.search-input {
  width: 100%;
  padding: 0.875rem 1rem 0.875rem 2.5rem;
  border: 2px solid var(--border-light);
  border-radius: 0.5rem;
  background: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 1rem;
  transition: all var(--transition-fast);
}

.search-input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.filters {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1rem;
  align-items: end;
}

.filter-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.filter-select {
  padding: 0.75rem;
  border: 1px solid var(--border-medium);
  border-radius: 0.5rem;
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: 0.875rem;
  transition: all var(--transition-fast);
}

.clear-filters-btn {
  background: var(--danger-color);
  color: var(--text-inverse);
  border: none;
  border-radius: 0.5rem;
  padding: 0.75rem 1rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.875rem;
  white-space: nowrap;
}

.clear-filters-btn:hover {
  background: #dc2626;
  transform: translateY(-1px);
}

/* Stats Section */
.stats-section {
  margin: 1rem 0;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
}

.stat-card {
  background: var(--bg-primary);
  border-radius: 1rem;
  padding: 1.5rem;
  display: flex;
  align-items: center;
  gap: 1rem;
  box-shadow: var(--shadow-md);
  border: 1px solid var(--border-light);
  transition: transform var(--transition-fast);
}

.stat-card:hover {
  transform: translateY(-2px);
}

.stat-icon {
  width: 3rem;
  height: 3rem;
  border-radius: 0.75rem;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  color: var(--text-inverse);
}

.stat-card:nth-child(1) .stat-icon {
  background: var(--primary-color);
}
.stat-card:nth-child(2) .stat-icon {
  background: var(--warning-color);
}
.stat-card:nth-child(3) .stat-icon {
  background: var(--success-color);
}
.stat-card:nth-child(4) .stat-icon {
  background: var(--danger-color);
}

.stat-info {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.stat-number {
  font-size: 1.875rem;
  font-weight: 700;
  color: var(--text-primary);
}

.stat-label {
  font-size: 0.875rem;
  color: var(--text-secondary);
  font-weight: 500;
}

/* Tasks Section */
.tasks-section {
  background: var(--bg-primary);
  border-radius: 1rem;
  padding: 1.5rem;
  box-shadow: var(--shadow-md);
  border: 1px solid var(--border-light);
}

.tasks-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border-light);
}

.tasks-header h2 {
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--text-primary);
}

.sort-select {
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--border-medium);
  border-radius: 0.5rem;
  background: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 0.875rem;
}

.tasks-container {
  display: grid;
  gap: 0.75rem;
}

/* Task Item */
.task-item {
  background: var(--bg-secondary);
  border: 1px solid var(--border-light);
  border-radius: 0.75rem;
  padding: 1rem;
  display: grid;
  grid-template-columns: auto 1fr auto;
  gap: 1rem;
  align-items: center;
  transition: all var(--transition-fast);
  cursor: grab;
  position: relative;
  overflow: hidden;
}

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

.task-item.dragging {
  opacity: 0.5;
  transform: rotate(2deg);
  cursor: grabbing;
}

.task-item.completed {
  opacity: 0.7;
}

.task-item.completed .task-content .task-title {
  text-decoration: line-through;
  color: var(--text-tertiary);
}

.task-item.overdue {
  border-left: 4px solid var(--danger-color);
}

.task-item::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background: var(--category-color);
}

.task-item[data-category="personal"]::before {
  background: var(--category-personal);
}
.task-item[data-category="work"]::before {
  background: var(--category-work);
}
.task-item[data-category="shopping"]::before {
  background: var(--category-shopping);
}
.task-item[data-category="health"]::before {
  background: var(--category-health);
}
.task-item[data-category="education"]::before {
  background: var(--category-education);
}

.task-checkbox {
  width: 1.25rem;
  height: 1.25rem;
  border: 2px solid var(--border-medium);
  border-radius: 0.25rem;
  cursor: pointer;
  position: relative;
  transition: all var(--transition-fast);
}

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

.task-checkbox.checked::after {
  content: "✓";
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  color: white;
  font-size: 0.75rem;
  font-weight: bold;
}

.task-content {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  min-width: 0;
}

.task-title {
  font-weight: 600;
  color: var(--text-primary);
  word-wrap: break-word;
}

.task-meta {
  display: flex;
  gap: 0.75rem;
  align-items: center;
  flex-wrap: wrap;
}

.task-category {
  padding: 0.25rem 0.5rem;
  border-radius: 1rem;
  font-size: 0.75rem;
  font-weight: 500;
  color: white;
  text-transform: capitalize;
}

.task-category.personal {
  background: var(--category-personal);
}
.task-category.work {
  background: var(--category-work);
}
.task-category.shopping {
  background: var(--category-shopping);
}
.task-category.health {
  background: var(--category-health);
}
.task-category.education {
  background: var(--category-education);
}

.task-priority {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  font-size: 0.75rem;
  font-weight: 500;
  text-transform: capitalize;
}

.task-priority.high {
  color: var(--priority-high);
}
.task-priority.medium {
  color: var(--priority-medium);
}
.task-priority.low {
  color: var(--priority-low);
}

.task-due-date {
  font-size: 0.75rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.task-due-date.overdue {
  color: var(--danger-color);
  font-weight: 600;
}

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

.task-action-btn {
  background: none;
  border: none;
  padding: 0.5rem;
  border-radius: 0.25rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  color: var(--text-secondary);
}

.task-action-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.task-action-btn.edit:hover {
  color: var(--primary-color);
}

.task-action-btn.delete:hover {
  color: var(--danger-color);
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: 3rem 1rem;
  color: var(--text-secondary);
}

.empty-state i {
  font-size: 3rem;
  margin-bottom: 1rem;
  color: var(--text-tertiary);
}

.empty-state h3 {
  font-size: 1.25rem;
  margin-bottom: 0.5rem;
}

/* Modal */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--bg-modal);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-normal);
}

.modal-overlay.active {
  opacity: 1;
  visibility: visible;
}

.modal {
  background: var(--bg-primary);
  border-radius: 1rem;
  box-shadow: var(--shadow-lg);
  width: 90%;
  max-width: 500px;
  max-height: 90vh;
  overflow-y: auto;
  transform: scale(0.9) translateY(-20px);
  transition: transform var(--transition-normal);
}

.modal-overlay.active .modal {
  transform: scale(1) translateY(0);
}

.modal-header {
  padding: 1.5rem;
  border-bottom: 1px solid var(--border-light);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.modal-header h3 {
  font-size: 1.25rem;
  font-weight: 600;
}

.modal-close {
  background: none;
  border: none;
  font-size: 1.25rem;
  cursor: pointer;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.modal-close:hover {
  color: var(--text-primary);
}

.modal-body {
  padding: 1.5rem;
  display: grid;
  gap: 1rem;
}

.modal-footer {
  padding: 1.5rem;
  border-top: 1px solid var(--border-light);
  display: flex;
  gap: 1rem;
  justify-content: flex-end;
}

.btn {
  padding: 0.75rem 1.5rem;
  border-radius: 0.5rem;
  border: none;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-primary {
  background: var(--primary-color);
  color: var(--text-inverse);
}

.btn-primary:hover {
  background: var(--primary-hover);
}

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 1px solid var(--border-medium);
}

.btn-secondary:hover {
  background: var(--border-medium);
}

/* Notifications */
.notification-container {
  position: fixed;
  top: 1rem;
  right: 1rem;
  z-index: 1100;
  display: grid;
  gap: 0.5rem;
}

.notification {
  background: var(--bg-primary);
  border: 1px solid var(--border-light);
  border-radius: 0.5rem;
  padding: 1rem;
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  gap: 0.75rem;
  min-width: 300px;
  transform: translateX(100%);
  transition: transform var(--transition-normal);
}

.notification.show {
  transform: translateX(0);
}

.notification.success {
  border-left: 4px solid var(--success-color);
}

.notification.error {
  border-left: 4px solid var(--danger-color);
}

.notification.warning {
  border-left: 4px solid var(--warning-color);
}

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

.notification.success .notification-icon {
  color: var(--success-color);
}

.notification.error .notification-icon {
  color: var(--danger-color);
}

.notification.warning .notification-icon {
  color: var(--warning-color);
}

.notification-content {
  flex: 1;
}

.notification-title {
  font-weight: 600;
  margin-bottom: 0.25rem;
}

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

.notification-close {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

.notification-close:hover {
  color: var(--text-primary);
}

/* Responsive Design */
@media (max-width: 768px) {
  .app-container {
    padding: 0 0.75rem;
  }

  .header {
    padding: 1rem 0;
    margin-bottom: 1.5rem;
  }

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

  .form-row {
    grid-template-columns: 1fr;
  }

  .form-details {
    grid-template-columns: 1fr;
  }

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

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

  .tasks-header {
    flex-direction: column;
    gap: 1rem;
    align-items: stretch;
  }

  .task-item {
    grid-template-columns: auto 1fr;
    gap: 0.75rem;
  }

  .task-actions {
    grid-column: 1 / -1;
    justify-content: flex-end;
    margin-top: 0.5rem;
    padding-top: 0.5rem;
    border-top: 1px solid var(--border-light);
  }

  .modal {
    margin: 1rem;
    width: calc(100% - 2rem);
  }

  .modal-footer {
    flex-direction: column;
  }

  .notification-container {
    left: 1rem;
    right: 1rem;
  }

  .notification {
    min-width: auto;
  }
}

@media (max-width: 480px) {
  .stats-grid {
    grid-template-columns: 1fr;
  }

  .task-meta {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.5rem;
  }
}

/* Drag and Drop Styles */
.drag-over {
  background: var(--bg-tertiary);
  border: 2px dashed var(--primary-color);
}

.drag-placeholder {
  height: 80px;
  background: var(--bg-tertiary);
  border: 2px dashed var(--border-medium);
  border-radius: 0.75rem;
  margin: 0.375rem 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-tertiary);
  font-style: italic;
}

/* Loading States */
.loading {
  position: relative;
  overflow: hidden;
}

.loading::after {
  content: "";
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(
    90deg,
    transparent,
    rgba(255, 255, 255, 0.2),
    transparent
  );
  animation: shimmer 1.5s infinite;
}

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

/* Focus Styles for Accessibility */
*:focus {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

button:focus,
input:focus,
select:focus {
  outline: none;
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.3);
}

/* Smooth Scrolling */
html {
  scroll-behavior: smooth;
}

/* Print Styles */
@media print {
  .add-task-section,
  .filters-section,
  .task-actions,
  .modal-overlay,
  .notification-container,
  .theme-toggle {
    display: none !important;
  }

  .task-item {
    break-inside: avoid;
    border: 1px solid #000;
    margin-bottom: 0.5rem;
  }
}