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

:root {
    /* Color Palette - Modern Dark Theme */
    --bg-primary: #0f0f23;
    --bg-secondary: #1a1a2e;
    --bg-card: rgba(26, 26, 46, 0.6);
    --bg-card-hover: rgba(26, 26, 46, 0.8);
    --bg-overlay: rgba(0, 0, 0, 0.7);
    
    /* Accent Colors */
    --accent-primary: #6366f1;
    --accent-secondary: #8b5cf6;
    --accent-success: #10b981;
    --accent-warning: #f59e0b;
    --accent-danger: #ef4444;
    
    /* Text Colors */
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    
    /* Border & Divider */
    --border-color: rgba(148, 163, 184, 0.1);
    --divider-color: rgba(148, 163, 184, 0.05);
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.6);
    
    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: linear-gradient(135deg, #0f0f23 0%, #1a1a2e 50%, #16213e 100%);
    background-attachment: fixed;
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

/* ===================================
   CONTAINER & LAYOUT
   =================================== */
.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: var(--spacing-xl);
}

/* Header */
.app-header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
    padding: var(--spacing-xl) 0;
}

.app-header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-sm);
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.125rem;
    font-weight: 400;
}

/* Main Content Layout */
.main-content {
    display: grid;
    grid-template-columns: 320px 1fr;
    gap: var(--spacing-xl);
    align-items: start;
}

@media (max-width: 1024px) {
    .main-content {
        grid-template-columns: 1fr;
    }
}

/* ===================================
   SIDEBAR - PREDEFINED TASKS
   =================================== */
.sidebar {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-lg);
    position: sticky;
    top: var(--spacing-xl);
    max-height: calc(100vh - 4rem);
    overflow-y: auto;
}

.sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-lg);
    padding-bottom: var(--spacing-md);
    border-bottom: 1px solid var(--divider-color);
}

.sidebar-header h2 {
    font-size: 1.25rem;
    font-weight: 600;
}

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

.category-item {
    background: rgba(99, 102, 241, 0.05);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    transition: all var(--transition-base);
}

.category-item:hover {
    background: rgba(99, 102, 241, 0.1);
    border-color: var(--accent-primary);
    transform: translateY(-2px);
}

.category-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-sm);
}

.category-name {
    font-weight: 600;
    font-size: 1rem;
    color: var(--text-primary);
}

.category-actions {
    display: flex;
    gap: var(--spacing-xs);
}

.predefined-task-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
    margin-top: var(--spacing-sm);
}

.predefined-task-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm);
    background: rgba(255, 255, 255, 0.02);
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    transition: all var(--transition-fast);
}

.predefined-task-item:hover {
    background: rgba(255, 255, 255, 0.05);
}

.predefined-task-actions {
    display: flex;
    gap: var(--spacing-xs);
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.predefined-task-item:hover .predefined-task-actions {
    opacity: 1;
}

/* ===================================
   TASK AREA - MAIN TASKS
   =================================== */
.task-area {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-lg);
    min-height: 500px;
}

.task-area-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-xl);
    padding-bottom: var(--spacing-md);
    border-bottom: 2px solid var(--divider-color);
}

.task-area-header h2 {
    font-size: 1.5rem;
    font-weight: 600;
}

/* Main Tasks Container */
.main-tasks-container {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

/* Main Task Card */
.main-task-card {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.05));
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    transition: all var(--transition-base);
    cursor: move;
}

.main-task-card:hover {
    border-color: var(--accent-primary);
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.2);
    transform: translateY(-2px);
}

.main-task-card.sortable-ghost {
    opacity: 0.4;
}

.main-task-card.sortable-drag {
    box-shadow: var(--shadow-xl);
}

.main-task-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

.drag-handle {
    font-size: 1.25rem;
    color: var(--text-muted);
    cursor: grab;
    transition: color var(--transition-fast);
}

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

.main-task-card:hover .drag-handle {
    color: var(--accent-primary);
}

.main-task-checkbox {
    width: 24px;
    height: 24px;
    cursor: pointer;
    accent-color: var(--accent-success);
}

.main-task-title {
    flex: 1;
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
}

.main-task-title.editable {
    cursor: text;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    transition: background var(--transition-fast);
}

.main-task-title.editable:hover {
    background: rgba(255, 255, 255, 0.05);
}

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

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

.task-progress {
    font-size: 0.875rem;
    color: var(--text-secondary);
    padding: 0.25rem 0.75rem;
    background: rgba(99, 102, 241, 0.1);
    border-radius: var(--radius-lg);
}

/* Subtasks Section */
.subtasks-section {
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--divider-color);
}

.subtasks-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.subtask-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.subtask-item:hover {
    background: rgba(255, 255, 255, 0.06);
    border-color: var(--accent-primary);
}

.subtask-checkbox {
    width: 18px;
    height: 18px;
    cursor: pointer;
    accent-color: var(--accent-success);
}

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

.subtask-title.completed {
    text-decoration: line-through;
    opacity: 0.6;
}

.subtask-badge {
    font-size: 0.75rem;
    padding: 0.125rem 0.5rem;
    background: rgba(139, 92, 246, 0.2);
    color: var(--accent-secondary);
    border-radius: var(--radius-sm);
    font-weight: 500;
}

.subtask-actions {
    display: flex;
    gap: var(--spacing-xs);
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.subtask-item:hover .subtask-actions {
    opacity: 1;
}

.subtask-add-section {
    display: flex;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-sm);
}

/* Empty State */
.empty-state {
    display: none;
    text-align: center;
    padding: var(--spacing-xl) 0;
}

.empty-state.visible {
    display: block;
}

.empty-icon {
    font-size: 4rem;
    margin-bottom: var(--spacing-md);
    opacity: 0.5;
}

.empty-state h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-sm);
    color: var(--text-secondary);
}

.empty-state p {
    color: var(--text-muted);
    margin-bottom: var(--spacing-lg);
}

/* ===================================
   BUTTONS
   =================================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    padding: 0.625rem 1.25rem;
    font-size: 0.9375rem;
    font-weight: 500;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-base);
    font-family: inherit;
    white-space: nowrap;
}

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

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

.btn-primary {
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    color: white;
}

.btn-primary:hover {
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.4);
}

.btn-success {
    background: linear-gradient(135deg, var(--accent-success), #059669);
    color: white;
}

.btn-success:hover {
    box-shadow: 0 0 20px rgba(16, 185, 129, 0.4);
}

.btn-secondary {
    background: rgba(148, 163, 184, 0.1);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: rgba(148, 163, 184, 0.2);
}

.btn-danger {
    background: var(--accent-danger);
    color: white;
}

.btn-danger:hover {
    box-shadow: 0 0 20px rgba(239, 68, 68, 0.4);
}

.btn-sm {
    padding: 0.375rem 0.75rem;
    font-size: 0.8125rem;
}

.btn-icon {
    padding: 0.5rem;
    width: 36px;
    height: 36px;
}

.btn-icon-sm {
    padding: 0.25rem;
    width: 28px;
    height: 28px;
    font-size: 0.875rem;
}

.icon {
    font-size: 1.125rem;
}

/* ===================================
   MODALS
   =================================== */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--bg-overlay);
    backdrop-filter: blur(5px);
    z-index: 1000;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-md);
    animation: fadeIn var(--transition-base);
}

.modal.active {
    display: flex;
}

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

.modal-content {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    width: 100%;
    max-width: 500px;
    box-shadow: var(--shadow-xl);
    animation: slideUp var(--transition-slow);
}

.modal-large .modal-content {
    max-width: 700px;
}

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

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

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

.btn-close {
    background: transparent;
    border: none;
    color: var(--text-secondary);
    font-size: 1.75rem;
    cursor: pointer;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.btn-close:hover {
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-primary);
}

.modal-body {
    padding: var(--spacing-lg);
}

.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: var(--spacing-sm);
    padding: var(--spacing-lg);
    border-top: 1px solid var(--divider-color);
}

/* ===================================
   FORMS
   =================================== */
.form-group {
    margin-bottom: var(--spacing-md);
}

.form-group:last-child {
    margin-bottom: 0;
}

.form-group label {
    display: block;
    margin-bottom: var(--spacing-xs);
    font-weight: 500;
    font-size: 0.9375rem;
    color: var(--text-secondary);
}

.form-control {
    width: 100%;
    padding: 0.75rem 1rem;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1rem;
    font-family: inherit;
    transition: all var(--transition-base);
}

.form-control:focus {
    outline: none;
    border-color: var(--accent-primary);
    background: rgba(255, 255, 255, 0.08);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.form-control::placeholder {
    color: var(--text-muted);
}

/* ===================================
   SCROLLBAR
   =================================== */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: rgba(0, 0, 0, 0.2);
    border-radius: var(--radius-sm);
}

::-webkit-scrollbar-thumb {
    background: rgba(148, 163, 184, 0.3);
    border-radius: var(--radius-sm);
}

::-webkit-scrollbar-thumb:hover {
    background: rgba(148, 163, 184, 0.5);
}

/* ===================================
   PREDEFINED TASKS LIST (Modal)
   =================================== */
#predefinedTasksList {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    max-height: 400px;
    overflow-y: auto;
}

.predefined-category-group {
    background: rgba(99, 102, 241, 0.05);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
}

.predefined-category-group h4 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--accent-primary);
}

.predefined-tasks-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: var(--spacing-sm);
}

.predefined-task-select-item {
    padding: var(--spacing-sm) var(--spacing-md);
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-size: 0.9375rem;
}

.predefined-task-select-item:hover {
    background: rgba(99, 102, 241, 0.1);
    border-color: var(--accent-primary);
    transform: scale(1.02);
}

/* ===================================
   ANIMATIONS
   =================================== */
@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.5;
    }
}

.loading {
    animation: pulse 1.5s ease-in-out infinite;
}