/* ToDo WebApp v4.0 - Added advanced task management (Favorites, Tags, Due Dates, Undo) */

:root {
  /* Light Mode Colors */
  --bg-gradient-start: #f0f4f8;
  --bg-gradient-end: #e8eef3;
  --container-bg: #ffffff;
  --text-primary: #2d3748;
  --text-secondary: #718096;
  --text-muted: #a0aec0;
  --accent-primary: #4299e1;
  --accent-primary-hover: #3182ce;
  --accent-success: #48bb78;
  --accent-warning: #ed8936;
  --accent-danger: #f56565;
  --accent-favorite: #ecc94b;
  --border-color: #e2e8f0;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.15);
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;
  --transition-slow: 350ms ease;
}

body.dark-mode {
  /* Dark Mode Colors */
  --bg-gradient-start: #1a202c;
  --bg-gradient-end: #2d3748;
  --container-bg: #2d3748;
  --text-primary: #e2e8f0;
  --text-secondary: #a0aec0;
  --text-muted: #718096;
  --accent-primary: #4299e1;
  --accent-primary-hover: #63b3ed;
  --accent-success: #48bb78;
  --accent-warning: #ed8936;
  --accent-danger: #fc8181;
  --accent-favorite: #f6e05e;
  --border-color: #4a5568;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.4);
}

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

body {
  background: linear-gradient(
    135deg,
    var(--bg-gradient-start) 0%,
    var(--bg-gradient-end) 100%
  );
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI",
    sans-serif;
  color: var(--text-primary);
  padding: 20px;
  transition: background var(--transition-normal);
}

.container {
  width: 100%;
  max-width: 600px;
  background: var(--container-bg);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  padding: 2rem;
  transition: background var(--transition-normal);
}

.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 2rem;
}

.header h1 {
  font-size: 1.875rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.5px;
}

.theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-secondary);
  padding: 0.5rem;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

.theme-toggle:hover {
  color: var(--accent-primary);
  background: var(--border-color);
}

.theme-toggle svg {
  width: 22px;
  height: 22px;
  stroke: currentColor;
}

.task-form {
  margin-bottom: 1.5rem;
}

.input-wrapper {
  display: flex;
  gap: 0.75rem;
}

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

#task-input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(66, 153, 225, 0.1);
}

#task-input::placeholder {
  color: var(--text-muted);
}

.btn-add {
  padding: 0.875rem 1.25rem;
  background: var(--accent-primary);
  color: white;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
}

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

.btn-add:active {
  transform: translateY(0);
}

.action-buttons {
  display: flex;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.btn-secondary {
  flex: 1;
  padding: 0.625rem 1rem;
  background: var(--container-bg);
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  transition: all var(--transition-fast);
}

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

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

.btn-secondary svg {
  stroke: currentColor;
}

.filters {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
  padding: 0.5rem;
  background: var(--bg-gradient-start);
  border-radius: var(--radius-md);
}

.filter-btn {
  flex: 1;
  padding: 0.625rem 1rem;
  background: transparent;
  color: var(--text-secondary);
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.filter-btn:hover {
  color: var(--text-primary);
  background: var(--container-bg);
}

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

.todos {
  min-height: 200px;
  max-height: 500px;
  overflow-y: auto;
  padding-right: 0.5rem;
}

.todos::-webkit-scrollbar {
  width: 8px;
}

.todos::-webkit-scrollbar-track {
  background: var(--bg-gradient-start);
  border-radius: 4px;
}

.todos::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 4px;
}

.todos::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

.no-todos {
  text-align: center;
  color: var(--text-muted);
  padding: 3rem 1rem;
  font-size: 1rem;
}

.todo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 1rem;
  margin-bottom: 0.75rem;
  background: var(--container-bg);
  border: 1px solid var(--border-color);
  border-left: 4px solid var(--accent-primary);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  position: relative;
  cursor: move;
}

.todo:hover {
  box-shadow: var(--shadow-sm);
  transform: translateX(2px);
}

.todo.completed {
  border-left-color: var(--accent-success);
  opacity: 0.7;
}

.todo.completed .todo-text {
  text-decoration: line-through;
  color: var(--text-muted);
}

.todo.overdue {
  border-left-color: var(--accent-danger);
}

.todo.due-soon {
  border-left-color: var(--accent-warning);
}

.todo.dragging {
  opacity: 0.5;
  transform: rotate(2deg);
  box-shadow: var(--shadow-lg);
  z-index: 1000;
}

.todo.drag-over-top {
  border-top: 3px solid var(--accent-primary);
}

.todo.drag-over-bottom {
  border-bottom: 3px solid var(--accent-primary);
}

.drag-handle {
  color: var(--text-muted);
  cursor: grab;
  padding: 0.25rem;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

.drag-handle:hover {
  color: var(--accent-primary);
  background: var(--border-color);
}

.drag-handle:active {
  cursor: grabbing;
}

.drag-handle svg {
  stroke: currentColor;
}

.todo-checkbox {
  width: 22px;
  height: 22px;
  min-width: 22px;
  border: 2px solid var(--border-color);
  border-radius: 50%;
  cursor: pointer;
  transition: all var(--transition-fast);
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
}

.todo-checkbox:hover {
  border-color: var(--accent-primary);
}

.todo.completed .todo-checkbox {
  background: var(--accent-success);
  border-color: var(--accent-success);
}

.todo.completed .todo-checkbox::after {
  content: "✓";
  color: white;
  font-size: 14px;
  font-weight: bold;
}

.todo-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  min-width: 0;
}

.todo-text {
  font-size: 1rem;
  color: var(--text-primary);
  word-break: break-word;
  cursor: pointer;
  line-height: 1.5;
}

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

.todo-tags {
  display: flex;
  gap: 0.375rem;
  flex-wrap: wrap;
}

.tag {
  padding: 0.25rem 0.625rem;
  background: var(--accent-primary);
  color: white;
  border-radius: 12px;
  font-size: 0.75rem;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.tag-remove {
  cursor: pointer;
  opacity: 0.7;
  transition: opacity var(--transition-fast);
}

.tag-remove:hover {
  opacity: 1;
}

.todo-due-date {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  font-size: 0.75rem;
  color: var(--text-secondary);
  padding: 0.25rem 0.5rem;
  background: var(--bg-gradient-start);
  border-radius: var(--radius-sm);
}

.todo-due-date.overdue {
  color: var(--accent-danger);
  background: rgba(245, 101, 101, 0.1);
}

.todo-due-date.due-soon {
  color: var(--accent-warning);
  background: rgba(237, 137, 54, 0.1);
}

.todo-due-date svg {
  width: 12px;
  height: 12px;
  stroke: currentColor;
}

.todo-actions {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

.todo-action {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  cursor: pointer;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.todo-action:hover {
  background: var(--border-color);
  color: var(--text-primary);
}

.todo-action.star-btn.starred {
  color: var(--accent-favorite);
}

.todo-action.star-btn.starred:hover {
  color: var(--accent-warning);
}

.todo-action.delete-btn:hover {
  color: var(--accent-danger);
  background: rgba(245, 101, 101, 0.1);
}

.todo-action svg {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  fill: none;
}

.todo-action.star-btn.starred svg {
  fill: currentColor;
}

.edit-input {
  flex: 1;
  padding: 0.5rem;
  border: 2px solid var(--accent-primary);
  border-radius: var(--radius-sm);
  font-size: 1rem;
  color: var(--text-primary);
  background: var(--container-bg);
  font-family: inherit;
}

.edit-input:focus {
  outline: none;
}

.celebration {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  animation: fadeIn var(--transition-normal);
}

.celebration.hidden {
  display: none;
}

.celebration-content {
  background: var(--container-bg);
  padding: 3rem 2rem;
  border-radius: var(--radius-lg);
  text-align: center;
  box-shadow: var(--shadow-lg);
  animation: slideUp var(--transition-slow);
  max-width: 400px;
}

.celebration-icon {
  font-size: 4rem;
  margin-bottom: 1rem;
  animation: bounce 1s infinite;
}

.celebration-content h2 {
  font-size: 1.5rem;
  color: var(--text-primary);
  margin-bottom: 0.5rem;
}

.celebration-content p {
  color: var(--text-secondary);
  font-size: 1rem;
}

.modal {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 20px;
}

.modal.hidden {
  display: none;
}

.modal-content {
  background: var(--container-bg);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  width: 100%;
  max-width: 400px;
  animation: slideUp var(--transition-normal);
}

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

.modal-header h3 {
  font-size: 1.25rem;
  color: var(--text-primary);
}

.modal-close {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-secondary);
  padding: 0.25rem;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

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

.modal-body {
  padding: 1.5rem;
}

#tag-input {
  width: 100%;
  padding: 0.75rem;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 1rem;
  color: var(--text-primary);
  background: var(--container-bg);
  margin-bottom: 1rem;
}

#tag-input:focus {
  outline: none;
  border-color: var(--accent-primary);
}

.tag-suggestions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tag-suggestion {
  padding: 0.5rem 1rem;
  background: var(--bg-gradient-start);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  cursor: pointer;
  font-size: 0.875rem;
  transition: all var(--transition-fast);
}

.tag-suggestion:hover {
  background: var(--accent-primary);
  color: white;
  border-color: var(--accent-primary);
}

.date-picker {
  position: absolute;
  background: var(--container-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem;
  box-shadow: var(--shadow-md);
  z-index: 100;
  animation: slideUp var(--transition-fast);
}

.date-picker.hidden {
  display: none;
}

#date-input {
  width: 100%;
  padding: 0.625rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  color: var(--text-primary);
  background: var(--container-bg);
  margin-bottom: 0.75rem;
}

#date-input:focus {
  outline: none;
  border-color: var(--accent-primary);
}

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

.btn-small {
  flex: 1;
  padding: 0.5rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  background: var(--container-bg);
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.btn-small:hover {
  background: var(--border-color);
  color: var(--text-primary);
}

.btn-small.btn-primary {
  background: var(--accent-primary);
  color: white;
  border-color: var(--accent-primary);
}

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

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

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

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

/* Responsive Design */
@media (max-width: 640px) {
  .container {
    padding: 1.5rem;
  }

  .header h1 {
    font-size: 1.5rem;
  }

  .input-wrapper {
    flex-direction: column;
  }

  .btn-add {
    width: 100%;
  }

  .action-buttons {
    flex-direction: column;
  }

  .filters {
    flex-wrap: wrap;
  }

  .filter-btn {
    flex: 1 1 calc(50% - 0.25rem);
  }

  .todo {
    padding: 0.875rem;
  }

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

  .drag-handle {
    display: none;
  }
}

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

@media (hover: none) and (pointer: coarse) {
  .todo {
    cursor: default;
  }

  .drag-handle {
    padding: 0.75rem;
    touch-action: none;
  }
}