/* ============================================
   CSS CUSTOM PROPERTIES (Variables)
   ============================================ */
:root {
  /* Light Mode Colors */
  --bg-primary: #ffffff;
  --bg-secondary: #f5f5f5;
  --bg-task: #ffffff;
  --text-primary: #333333;
  --text-secondary: #666666;
  --text-placeholder: #999999;
  --border-color: #e0e0e0;
  --accent-color: #4CAF50;
  --accent-hover: #45a049;
  --delete-color: #f44336;
  --delete-hover: #da190b;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  --shadow-hover: 0 4px 12px rgba(0, 0, 0, 0.15);
  --shadow-strong: 0 8px 24px rgba(0, 0, 0, 0.2);

  /* Spacing */
  --spacing-xs: 4px;
  --spacing-sm: 8px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;

  /* Typography */
  --font-family: Cochin, serif;
  --font-size-base: 16px;
  --font-size-lg: 18px;
  --font-size-xl: 24px;
  --font-size-sm: 14px;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-medium: 0.3s ease;

  /* Touch Targets */
  --touch-target-min: 44px;

  /* Border Radius */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
}

/* Dark Mode Variables */
[data-theme="dark"] {
  --bg-primary: #1a1a1a;
  --bg-secondary: #2d2d2d;
  --bg-task: #2d2d2d;
  --text-primary: #e0e0e0;
  --text-secondary: #a0a0a0;
  --text-placeholder: #707070;
  --border-color: #404040;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-hover: 0 4px 12px rgba(0, 0, 0, 0.4);
  --shadow-strong: 0 8px 24px rgba(0, 0, 0, 0.6);
}

/* ============================================
   BASE STYLES
   ============================================ */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background var(--transition-medium), color var(--transition-medium);
  -webkit-tap-highlight-color: transparent;
  overflow-x: hidden;
}

/* ============================================
   APP CONTAINER
   ============================================ */
.app-container {
  max-width: 100vw;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background: var(--bg-primary);
}

/* ============================================
   HEADER
   ============================================ */
.app-header {
  position: relative;
  background: var(--bg-secondary);
  padding: var(--spacing-md);
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  box-shadow: var(--shadow);
  transition: background var(--transition-medium);
}

.app-header h1 {
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--text-primary);
  flex: 1;
  text-align: center;
  margin-right: 50px;
}

/* ============================================
   DARK MODE TOGGLE SWITCH
   ============================================ */
.dark-mode-toggle {
  display: flex;
  align-items: center;
}

.toggle-switch {
  position: relative;
  display: inline-block;
  width: 50px;
  height: 28px;
  cursor: pointer;
}

.toggle-switch input[type="checkbox"] {
  opacity: 0;
  width: 0;
  height: 0;
  position: absolute;
}

.toggle-slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #ccc;
  border-radius: 28px;
  transition: background-color var(--transition-medium);
}

.toggle-slider::before {
  position: absolute;
  content: "";
  height: 22px;
  width: 22px;
  left: 3px;
  bottom: 3px;
  background-color: white;
  border-radius: 50%;
  transition: transform var(--transition-medium);
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.toggle-switch input:checked + .toggle-slider {
  background-color: var(--accent-color);
}

.toggle-switch input:checked + .toggle-slider::before {
  transform: translateX(22px);
}

.toggle-switch input:focus-visible + .toggle-slider {
  box-shadow: 0 0 0 3px rgba(76, 175, 80, 0.3);
  outline: none;
}

/* ============================================
   ADD TASK SECTION
   ============================================ */
.add-task-section {
  padding: var(--spacing-lg);
  background: var(--bg-primary);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

#taskInput {
  width: 100%;
  padding: var(--spacing-md);
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  background: var(--bg-task);
  color: var(--text-primary);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  resize: vertical;
  min-height: 80px;
  transition: border-color var(--transition-fast), background var(--transition-medium);
}

#taskInput::placeholder {
  color: var(--text-placeholder);
}

#taskInput:focus {
  outline: none;
  border-color: var(--accent-color);
}

.btn-primary {
  width: 100%;
  min-height: var(--touch-target-min);
  padding: var(--spacing-md) var(--spacing-lg);
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  font-weight: 600;
  color: white;
  background: var(--accent-color);
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: background var(--transition-fast), transform var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

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

.btn-primary:active {
  transform: scale(0.98);
}

.btn-primary:focus-visible {
  outline: 3px solid rgba(76, 175, 80, 0.3);
  outline-offset: 2px;
}

/* ============================================
   TASKS SECTION
   ============================================ */
.tasks-section {
  flex: 1;
  padding: var(--spacing-lg);
  overflow-y: auto;
  background: var(--bg-primary);
}

.tasks-list {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

/* ============================================
   EMPTY STATE
   ============================================ */
.empty-state {
  display: none;
  text-align: center;
  padding: var(--spacing-xl);
  color: var(--text-secondary);
  font-size: var(--font-size-base);
}

.empty-state p {
  margin: 0;
}

/* ============================================
   TASK ITEM
   ============================================ */
.task-item {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--spacing-md);
  padding: var(--spacing-md);
  background: var(--bg-task);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  cursor: pointer;
  user-select: none;
  -webkit-user-select: none;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-medium);
  box-shadow: var(--shadow);
}

.task-item:hover {
  box-shadow: var(--shadow-hover);
}

.task-item.pressing {
  transform: scale(0.98);
  box-shadow: var(--shadow-hover);
}

.task-item.completed .task-text {
  text-decoration: line-through;
  opacity: 0.6;
}

/* ============================================
   CUSTOM CHECKBOX
   ============================================ */
.task-checkbox {
  appearance: none;
  -webkit-appearance: none;
  width: 24px;
  height: 24px;
  min-width: 24px;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-sm);
  cursor: pointer;
  position: relative;
  transition: all var(--transition-fast);
  background: var(--bg-task);
  margin-top: 2px;
}

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

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

.task-checkbox:checked::after {
  content: '';
  position: absolute;
  left: 7px;
  top: 3px;
  width: 6px;
  height: 12px;
  border: solid white;
  border-width: 0 2px 2px 0;
  transform: rotate(45deg);
}

.task-checkbox:focus-visible {
  outline: 3px solid rgba(76, 175, 80, 0.3);
  outline-offset: 2px;
}

/* Expanded touch target */
.task-checkbox::before {
  content: '';
  position: absolute;
  top: -10px;
  left: -10px;
  right: -10px;
  bottom: -10px;
}

/* ============================================
   TASK TEXT
   ============================================ */
.task-text {
  font-size: var(--font-size-base);
  color: var(--text-primary);
  word-wrap: break-word;
  overflow-wrap: break-word;
  hyphens: auto;
  white-space: pre-wrap;
  line-height: 1.5;
}

/* ============================================
   TASK EDIT TEXTAREA
   ============================================ */
.task-edit-textarea {
  width: 100%;
  padding: var(--spacing-sm);
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  background: var(--bg-primary);
  color: var(--text-primary);
  border: 2px solid var(--accent-color);
  border-radius: var(--radius-sm);
  resize: vertical;
  min-height: 60px;
  line-height: 1.5;
}

.task-edit-textarea:focus {
  outline: none;
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px rgba(76, 175, 80, 0.2);
}

/* ============================================
   CONTEXT MENU
   ============================================ */
.context-menu {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background: var(--bg-task);
  border-radius: var(--radius-xl) var(--radius-xl) 0 0;
  padding: var(--spacing-md);
  transform: translateY(100%);
  transition: transform var(--transition-medium);
  z-index: 1000;
  box-shadow: var(--shadow-strong);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.context-menu.active {
  transform: translateY(0);
}

.menu-item {
  width: 100%;
  min-height: var(--touch-target-min);
  padding: var(--spacing-md);
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  font-weight: 500;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: background var(--transition-fast), transform var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

.menu-item-edit {
  background: var(--accent-color);
  color: white;
}

.menu-item-edit:hover {
  background: var(--accent-hover);
}

.menu-item-delete {
  background: var(--delete-color);
  color: white;
}

.menu-item-delete:hover {
  background: var(--delete-hover);
}

.menu-item-cancel {
  background: var(--bg-secondary);
  color: var(--text-primary);
}

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

.menu-item:active {
  transform: scale(0.98);
}

.menu-item:focus-visible {
  outline: 3px solid rgba(76, 175, 80, 0.3);
  outline-offset: 2px;
}

/* ============================================
   BACKDROP
   ============================================ */
.backdrop {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--transition-medium), visibility var(--transition-medium);
  z-index: 999;
}

.backdrop.active {
  opacity: 1;
  visibility: visible;
}

/* ============================================
   RESPONSIVE DESIGN - TABLET AND DESKTOP
   ============================================ */
@media (min-width: 768px) {
  .app-container {
    max-width: 600px;
    margin: 0 auto;
    box-shadow: var(--shadow-strong);
    min-height: 100vh;
  }

  .app-header h1 {
    font-size: 28px;
  }

  .add-task-section {
    padding: var(--spacing-xl);
  }

  .tasks-section {
    padding: 0 var(--spacing-xl) var(--spacing-xl);
  }

  /* Context menu becomes centered modal on desktop */
  .context-menu {
    bottom: auto;
    left: 50%;
    top: 50%;
    right: auto;
    width: 400px;
    transform: translate(-50%, -50%) scale(0.9);
    opacity: 0;
    border-radius: var(--radius-lg);
  }

  .context-menu.active {
    transform: translate(-50%, -50%) scale(1);
    opacity: 1;
  }
}

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

/* ============================================
   FOCUS STYLES FOR KEYBOARD NAVIGATION
   ============================================ */
button:focus:not(:focus-visible),
input:focus:not(:focus-visible),
textarea:focus:not(:focus-visible) {
  outline: none;
}

button:focus-visible,
input:focus-visible,
textarea:focus-visible {
  outline: 3px solid rgba(76, 175, 80, 0.3);
  outline-offset: 2px;
}

/* ============================================
   SCROLLBAR STYLING
   ============================================ */
.tasks-section::-webkit-scrollbar {
  width: 8px;
}

.tasks-section::-webkit-scrollbar-track {
  background: var(--bg-primary);
}

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

.tasks-section::-webkit-scrollbar-thumb:hover {
  background: var(--text-secondary);
}