:root {
            /* Color System */
            --primary-100: #EBF5FF;
            --primary-500: #007AFF;
            --primary-700: #0056B3;
            --neutral-50: #F8F9FA;
            --neutral-100: #FFFFFF;
            --neutral-400: #868E96;
            --neutral-700: #495057;
            --neutral-900: #212529;
            --success: #28A745;
            --warning: #FFC107;
            --error: #DC3545;
            
            /* Spacing */
            --space-xs: 4px;
            --space-sm: 8px;
            --space-md: 12px;
            --space-lg: 16px;
            --space-xl: 24px;
            --space-xxl: 32px;
            
            /* Radius */
            --radius-md: 8px;
            --radius-lg: 12px;
            
            /* Shadows */
            --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
            --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
            --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.12);
        }

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

        body {
            font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
            background-color: var(--neutral-50);
            color: var(--neutral-700);
            line-height: 1.6;
            font-size: 14px;
            min-height: 100vh;
        }

        /* Header */
        .header {
            background: var(--neutral-100);
            border-bottom: 1px solid rgba(0, 0, 0, 0.05);
            padding: var(--space-lg) var(--space-xxl);
            position: sticky;
            top: 0;
            z-index: 100;
        }

        .header-content {
            max-width: 1400px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
            gap: var(--space-xl);
        }

        .header h1 {
            font-size: 30px;
            font-weight: 700;
            line-height: 1.2;
            color: var(--neutral-900);
        }

        .header-actions {
            display: flex;
            gap: var(--space-lg);
            align-items: center;
        }

        /* Search and Filter */
        .search-container {
            position: relative;
        }

        .search-input {
            width: 280px;
            height: 44px;
            background: var(--neutral-100);
            border: 1px solid var(--neutral-400);
            border-radius: var(--radius-md);
            padding: 0 var(--space-lg);
            font-size: 14px;
            color: var(--neutral-700);
            transition: border-color 200ms ease, box-shadow 200ms ease;
        }

        .search-input:focus {
            outline: none;
            border-color: var(--primary-500);
            box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.2);
        }

        .filter-select {
            height: 44px;
            background: var(--neutral-100);
            border: 1px solid var(--neutral-400);
            border-radius: var(--radius-md);
            padding: 0 var(--space-lg);
            font-size: 14px;
            color: var(--neutral-700);
            cursor: pointer;
            transition: border-color 200ms ease, box-shadow 200ms ease;
        }

        .filter-select:focus {
            outline: none;
            border-color: var(--primary-500);
            box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.2);
        }

        /* Buttons */
        .btn {
            height: 44px;
            padding: 0 var(--space-xl);
            border: none;
            border-radius: var(--radius-md);
            font-size: 14px;
            font-weight: 600;
            cursor: pointer;
            transition: all 200ms ease;
            display: flex;
            align-items: center;
            gap: var(--space-sm);
        }

        .btn-primary {
            background: var(--primary-500);
            color: var(--neutral-100);
        }

        .btn-primary:hover {
            background: var(--primary-700);
        }

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

        /* Main Content */
        .main-content {
            max-width: 1400px;
            margin: 0 auto;
            padding: var(--space-xxl);
        }

        /* Project Selector */
        .project-selector {
            margin-bottom: var(--space-xxl);
        }

        .project-selector label {
            display: block;
            font-weight: 600;
            color: var(--neutral-900);
            margin-bottom: var(--space-sm);
        }

        .project-select {
            width: 100%;
            max-width: 400px;
            height: 44px;
            background: var(--neutral-100);
            border: 1px solid var(--neutral-400);
            border-radius: var(--radius-md);
            padding: 0 var(--space-lg);
            font-size: 14px;
            color: var(--neutral-700);
            cursor: pointer;
        }

        .project-select:focus {
            outline: none;
            border-color: var(--primary-500);
            box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.2);
        }

        /* Kanban Board */
        .kanban-board {
            display: flex;
            gap: var(--space-xl);
            overflow-x: auto;
            padding-bottom: var(--space-lg);
            min-height: calc(100vh - 200px);
        }

        .kanban-column {
            flex: 1;
            min-width: 320px;
            background: var(--neutral-100);
            border-radius: var(--radius-lg);
            box-shadow: var(--shadow-sm);
            border: 1px solid rgba(0, 0, 0, 0.05);
            transition: background-color 200ms ease-out;
        }

        .kanban-column.drag-over {
            background: var(--primary-100);
        }

        .column-header {
            padding: var(--space-lg);
            border-bottom: 1px solid rgba(0, 0, 0, 0.05);
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

        .column-title {
            font-size: 16px;
            font-weight: 600;
            line-height: 1.4;
            color: var(--neutral-900);
            text-transform: uppercase;
            letter-spacing: 0.05em;
        }

        .task-count {
            font-size: 12px;
            color: var(--neutral-400);
            font-weight: 400;
        }

        .column-body {
            padding: var(--space-sm);
            display: flex;
            flex-direction: column;
            gap: var(--space-md);
            min-height: 400px;
        }

        /* Task Cards */
        .task-card {
            background: var(--neutral-100);
            border: 1px solid rgba(0, 0, 0, 0.05);
            border-radius: var(--radius-md);
            padding: var(--space-lg);
            box-shadow: var(--shadow-sm);
            cursor: pointer;
            transition: all 250ms ease-out;
            position: relative;
            overflow: hidden;
        }

        .task-card::before {
            content: '';
            position: absolute;
            left: 0;
            top: 0;
            width: 4px;
            height: 100%;
            border-radius: 0 2px 2px 0;
        }

        .task-card.deadline-upcoming::before {
            background: var(--warning);
        }

        .task-card.deadline-overdue::before {
            background: var(--error);
        }

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

        .task-card.dragging {
            transform: rotate(3deg) scale(1.05);
            box-shadow: var(--shadow-lg);
            opacity: 0.95;
            z-index: 1000;
        }

        .task-title {
            font-size: 16px;
            font-weight: 500;
            line-height: 1.5;
            color: var(--neutral-900);
            margin-bottom: var(--space-sm);
        }

        .task-description {
            font-size: 14px;
            color: var(--neutral-700);
            line-height: 1.6;
            margin-bottom: var(--space-md);
            display: -webkit-box;
            -webkit-line-clamp: 2;
            -webkit-box-orient: vertical;
            overflow: hidden;
        }

        .task-meta {
            display: flex;
            justify-content: space-between;
            align-items: center;
            font-size: 12px;
            color: var(--neutral-400);
        }

        .task-date {
            display: flex;
            align-items: center;
            gap: var(--space-xs);
        }

        .deadline-badge {
            padding: 2px var(--space-sm);
            border-radius: var(--radius-sm);
            font-size: 11px;
            font-weight: 500;
            text-transform: uppercase;
            letter-spacing: 0.05em;
        }

        .deadline-badge.upcoming {
            background: rgba(255, 193, 7, 0.1);
            color: var(--warning);
        }

        .deadline-badge.overdue {
            background: rgba(220, 53, 69, 0.1);
            color: var(--error);
        }

        /* Modals */
        .modal-overlay {
            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;
            opacity: 0;
            visibility: hidden;
            transition: all 200ms ease;
        }

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

        .modal {
            background: var(--neutral-100);
            border-radius: var(--radius-lg);
            box-shadow: var(--shadow-lg);
            max-width: 500px;
            width: 90%;
            max-height: 90vh;
            overflow-y: auto;
            transform: scale(0.9) translateY(20px);
            transition: transform 200ms ease;
        }

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

        .modal-header {
            padding: var(--space-xl);
            border-bottom: 1px solid rgba(0, 0, 0, 0.05);
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

        .modal-title {
            font-size: 20px;
            font-weight: 600;
            color: var(--neutral-900);
        }

        .modal-close {
            background: none;
            border: none;
            font-size: 24px;
            color: var(--neutral-400);
            cursor: pointer;
            padding: var(--space-sm);
            border-radius: var(--radius-md);
            transition: all 200ms ease;
        }

        .modal-close:hover {
            background: var(--neutral-50);
            color: var(--neutral-700);
        }

        .modal-body {
            padding: var(--space-xl);
        }

        .form-group {
            margin-bottom: var(--space-lg);
        }

        .form-label {
            display: block;
            font-weight: 600;
            color: var(--neutral-900);
            margin-bottom: var(--space-sm);
        }

        .form-input,
        .form-textarea,
        .form-select {
            width: 100%;
            height: 44px;
            background: var(--neutral-100);
            border: 1px solid var(--neutral-400);
            border-radius: var(--radius-md);
            padding: 0 var(--space-lg);
            font-size: 14px;
            color: var(--neutral-700);
            transition: border-color 200ms ease, box-shadow 200ms ease;
        }

        .form-textarea {
            height: 100px;
            resize: vertical;
            padding: var(--space-lg);
        }

        .form-input:focus,
        .form-textarea:focus,
        .form-select:focus {
            outline: none;
            border-color: var(--primary-500);
            box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.2);
        }

        .modal-footer {
            padding: var(--space-xl);
            border-top: 1px solid rgba(0, 0, 0, 0.05);
            display: flex;
            gap: var(--space-lg);
            justify-content: flex-end;
        }

        /* Toast Notifications */
        .toast-container {
            position: fixed;
            top: var(--space-xl);
            right: var(--space-xl);
            z-index: 2000;
            display: flex;
            flex-direction: column;
            gap: var(--space-sm);
        }

        .toast {
            background: var(--neutral-100);
            border-radius: var(--radius-md);
            box-shadow: var(--shadow-lg);
            padding: var(--space-lg);
            min-width: 300px;
            border-left: 4px solid var(--primary-500);
            transform: translateX(100%);
            transition: transform 300ms ease;
        }

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

        .toast.success {
            border-left-color: var(--success);
        }

        .toast.error {
            border-left-color: var(--error);
        }

        /* Empty State */
        .empty-state {
            text-align: center;
            padding: var(--space-xxl);
            color: var(--neutral-400);
        }

        .empty-state-icon {
            font-size: 48px;
            margin-bottom: var(--space-lg);
        }

        .empty-state-title {
            font-size: 18px;
            font-weight: 600;
            color: var(--neutral-700);
            margin-bottom: var(--space-sm);
        }

        .empty-state-text {
            font-size: 14px;
            line-height: 1.6;
        }

        /* Responsive Design */
        @media (max-width: 768px) {
            .header-content {
                flex-direction: column;
                align-items: stretch;
                gap: var(--space-lg);
            }

            .header-actions {
                justify-content: stretch;
            }

            .search-input {
                width: 100%;
            }

            .kanban-board {
                overflow-x: auto;
                padding-bottom: var(--space-md);
            }

            .kanban-column {
                min-width: 300px;
            }

            .modal {
                width: 95%;
                margin: var(--space-lg);
            }
        }