:root {
            --primary-color: #4361ee;
            --secondary-color: #3a0ca3;
            --accent-color: #7209b7;
            --light-gray: #f8f9fa;
            --border-color: #eaeaea;
            --text-color: #333;
            --text-muted: #6c757d;
            --success-color: #4cc9f0;
            --warning-color: #f72585;
            --danger-color: #dc3545;
            --tile-1: #4361ee;
            --tile-2: #3a0ca3;
            --tile-3: #7209b7;
            --tile-4: #f72585;
            --tile-5: #4cc9f0;
            --tile-6: #4895ef;
            --tile-7: #560bad;
            --tile-8: #480ca8;
            --tile-9: #3f37c9;
            --tile-10: #4361ee;
            --tile-11: #3a0ca3;
            --tile-12: #7209b7;
            --tile-13: #f72585;
            --tile-14: #4cc9f0;
            --tile-15: #4895ef;
            --empty-color: #adb5bd;
        }
         
        .page-header {
            background: linear-gradient(135deg, rgba(67, 97, 238, 0.1) 0%, rgba(58, 12, 163, 0.1) 100%);
            padding: 1.5rem 0;
            margin-bottom: 2rem;
            border-bottom: 1px solid rgba(67, 97, 238, 0.2);
            position: relative;
            overflow: hidden;   color: var(--text-color);
        }
    
        .breadcrumb {
            background-color: transparent;
            padding: 0.5rem 0;
            margin-bottom: 0.5rem;
        }
        
        .breadcrumb-item a {
            color: var(--text-muted);
            text-decoration: none;
        }
        
        .breadcrumb-item.active {
            color: var(--text-color);
        }
          
        .game-area {
            display: flex;
            flex-direction: column;
            align-items: center;
            margin: 2rem 0;
        }
        
        .puzzle-container {
            width: 100%;
            max-width: 600px;
            height: 600px;
            background-color: #f5f5f5;
            border-radius: 10px;
            position: relative;
            overflow: hidden;
            margin-bottom: 2rem;
            border: 1px solid var(--border-color);
            display: flex;
            justify-content: center;
            align-items: center;
        }
        
        .puzzle-board {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            grid-template-rows: repeat(4, 1fr);
            gap: 5px;
            width: 500px;
            height: 500px;
            background-color: var(--empty-color);
            border-radius: 8px;
            padding: 5px;
            box-shadow: 0 5px 15px rgba(0,0,0,0.1);
        }
        
        .puzzle-tile {
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 2.5rem;
            font-weight: bold;
            color: white;
            border-radius: 6px;
            cursor: pointer;
            transition: all 0.3s ease;
            box-shadow: 0 3px 5px rgba(0,0,0,0.2);
            user-select: none;
            position: relative;
            overflow: hidden;
        }
        
        .puzzle-tile::before {
            content: "";
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background: linear-gradient(135deg, rgba(255,255,255,0.3) 0%, rgba(255,255,255,0.1) 50%, rgba(0,0,0,0.1) 100%);
            border-radius: 6px;
            pointer-events: none;
        }
        
        .puzzle-tile:hover {
            transform: translateY(-2px);
            box-shadow: 0 5px 10px rgba(0,0,0,0.2);
        }
        
        .puzzle-tile.empty {
            background-color: transparent;
            box-shadow: none;
            cursor: default;
        }
        
        .puzzle-tile.empty:hover {
            transform: none;
            box-shadow: none;
        }
        
        .puzzle-tile.empty::before {
            display: none;
        }
        
        .puzzle-tile.tile-1 { background-color: var(--tile-1); }
        .puzzle-tile.tile-2 { background-color: var(--tile-2); }
        .puzzle-tile.tile-3 { background-color: var(--tile-3); }
        .puzzle-tile.tile-4 { background-color: var(--tile-4); }
        .puzzle-tile.tile-5 { background-color: var(--tile-5); }
        .puzzle-tile.tile-6 { background-color: var(--tile-6); }
        .puzzle-tile.tile-7 { background-color: var(--tile-7); }
        .puzzle-tile.tile-8 { background-color: var(--tile-8); }
        .puzzle-tile.tile-9 { background-color: var(--tile-9); }
        .puzzle-tile.tile-10 { background-color: var(--tile-10); }
        .puzzle-tile.tile-11 { background-color: var(--tile-11); }
        .puzzle-tile.tile-12 { background-color: var(--tile-12); }
        .puzzle-tile.tile-13 { background-color: var(--tile-13); }
        .puzzle-tile.tile-14 { background-color: var(--tile-14); }
        .puzzle-tile.tile-15 { background-color: var(--tile-15); }
        
        .puzzle-info {
            display: flex;
            justify-content: space-between;
            align-items: center;
            width: 100%;
            max-width: 500px;
            margin-bottom: 1.5rem;
        }
        
        .puzzle-size-selector {
            display: flex;
            gap: 0.5rem;
        }
        
        .size-btn {
            padding: 0.5rem 1rem;
            border-radius: 6px;
            background-color: white;
            border: 2px solid var(--border-color);
            font-weight: 600;
            transition: all 0.3s;
        }
        
        .size-btn:hover {
            background-color: var(--light-gray);
        }
        
        .size-btn.active {
            background-color: var(--primary-color);
            color: white;
            border-color: var(--primary-color);
        }
        
        .game-controls {
            display: flex;
            flex-wrap: wrap;
            justify-content: center;
            gap: 1rem;
            margin: 1.5rem 0;
        }
        
        .game-btn {
            padding: 0.75rem 1.5rem;
            border-radius: 6px;
            font-weight: 600;
            transition: all 0.3s;
            border: none;
        }
        
        .game-btn-primary {
            background-color: var(--primary-color);
            color: white;
        }
        
        .game-btn-primary:hover {
            background-color: var(--secondary-color);
            transform: translateY(-2px);
        }
        
        .game-btn-secondary {
            background-color: #6c757d;
            color: white;
        }
        
        .game-btn-secondary:hover {
            background-color: #5a6268;
            transform: translateY(-2px);
        }
        
        .game-btn-success {
            background-color: var(--success-color);
            color: white;
        }
        
        .game-btn-success:hover {
            background-color: #3ab0d5;
            transform: translateY(-2px);
        }
        
        .game-btn-warning {
            background-color: var(--warning-color);
            color: white;
        }
        
        .game-btn-warning:hover {
            background-color: #d41c6c;
            transform: translateY(-2px);
        }
        
        .game-stats {
            display: flex;
            justify-content: space-around;
            background-color: var(--light-gray);
            border-radius: 8px;
            padding: 1.5rem;
            margin: 1.5rem 0;
            border: 1px solid var(--border-color);
        }
        
        .stat-item {
            text-align: center;
        }
        
        .stat-value {
            font-size: 2rem;
            font-weight: 700;
            color: var(--primary-color);
            margin-bottom: 0.25rem;
        }
        
        .stat-label {
            color: var(--text-muted);
            font-size: 0.9rem;
        }
        
        .game-info-box {
            background-color: rgba(67, 97, 238, 0.05);
            border-left: 3px solid var(--primary-color);
            padding: 1rem;
            border-radius: 0 4px 4px 0;
            margin: 1.5rem 0;
        }
        
        .game-tip-box {
            background-color: rgba(247, 37, 133, 0.05);
            border-left: 3px solid var(--warning-color);
            padding: 1rem;
            border-radius: 0 4px 4px 0;
            margin: 1.5rem 0;
        }
        
        .victory-message {
            background: linear-gradient(135deg, rgba(76, 201, 240, 0.1) 0%, rgba(76, 201, 240, 0.3) 100%);
            border: 2px solid var(--success-color);
            border-radius: 8px;
            padding: 2rem;
            text-align: center;
            margin: 2rem 0;
            display: none;
        }
        
        .victory-title {
            font-size: 2rem;
            font-weight: 700;
            color: var(--success-color);
            margin-bottom: 1rem;
        }
         
        .difficulty-indicator {
            display: inline-block;
            padding: 0.25rem 0.75rem;
            border-radius: 20px;
            font-size: 0.85rem;
            font-weight: 500;
            margin-right: 0.5rem;
        }
        
        .difficulty-easy {
            background-color: rgba(76, 201, 240, 0.1);
            color: #4cc9f0;
        }
        
        .difficulty-medium {
            background-color: rgba(247, 37, 133, 0.1);
            color: #f72585;
        }
        
        .difficulty-hard {
            background-color: rgba(114, 9, 183, 0.1);
            color: #7209b7;
        }
         
        .move-history {
            background-color: var(--light-gray);
            border-radius: 8px;
            padding: 1.5rem;
            margin: 1.5rem 0;
            max-height: 300px;
            overflow-y: auto;
            border: 1px solid var(--border-color);
        }
        
        .move-history-title {
            font-weight: 600;
            margin-bottom: 1rem;
            color: var(--primary-color);
        }
        
        .move-list {
            display: flex;
            flex-direction: column;
            gap: 0.5rem;
        }
        
        .move-item {
            padding: 0.5rem;
            background-color: white;
            border-radius: 4px;
            border-left: 3px solid var(--primary-color);
            font-family: monospace;
        }
        
        .move-item.current {
            background-color: rgba(67, 97, 238, 0.1);
            font-weight: bold;
        }
        
        .strategy-tips {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
            gap: 1rem;
            margin: 1.5rem 0;
        }
        
        .tip-card {
            background: white;
            border-radius: 8px;
            padding: 1.25rem;
            border: 1px solid var(--border-color);
            box-shadow: 0 2px 4px rgba(0,0,0,0.05);
        }
        
        .tip-icon {
            width: 48px;
            height: 48px;
            border-radius: 8px;
            background-color: rgba(67, 97, 238, 0.1);
            display: flex;
            align-items: center;
            justify-content: center;
            margin-bottom: 1rem;
            color: var(--primary-color);
            font-size: 1.25rem;
        }
        
        .tip-title {
            font-weight: 600;
            margin-bottom: 0.5rem;
            color: var(--text-color);
        }
        
        .tip-desc {
            color: var(--text-muted);
            font-size: 0.9rem;
        }
        
        @media (max-width: 768px) {
            .tool-card {
                padding: 1.5rem;
            }
            
            .puzzle-container {
                height: 500px;
            }
            
            .puzzle-board {
                width: 400px;
                height: 400px;
            }
            
            .puzzle-tile {
                font-size: 2rem;
            }
            
            .game-controls {
                flex-direction: column;
                align-items: center;
            }
            
            .game-btn {
                width: 100%;
                max-width: 300px;
            }
            
            .game-stats {
                flex-direction: column;
                gap: 1rem;
            }
        }
        
        @media (max-width: 480px) {
            .puzzle-container {
                height: 400px;
            }
            
            .puzzle-board {
                width: 350px;
                height: 350px;
            }
            
            .puzzle-tile {
                font-size: 1.5rem;
            }
        }
        
        .toast-container {
            position: fixed;
            bottom: 20px;
            right: 20px;
            z-index: 1050;
        }
        
        @keyframes pulse {
            0% { transform: scale(1); }
            50% { transform: scale(1.1); }
            100% { transform: scale(1); }
        }
        
        .pulse {
            animation: pulse 0.5s ease;
        }
        
        @keyframes slide-in {
            from { transform: translateY(-20px); opacity: 0; }
            to { transform: translateY(0); opacity: 1; }
        }
        
        .slide-in {
            animation: slide-in 0.3s ease;
        }
        
        .btn {
            border-radius: 6px;
            padding: 0.75rem 1.5rem;
            font-weight: 600;
            transition: all 0.3s;
        }
        
        .btn-primary {
            background-color: var(--primary-color);
            border-color: var(--primary-color);
        }
        
        .btn-primary:hover {
            background-color: var(--secondary-color);
            border-color: var(--secondary-color);
            transform: translateY(-1px);
        }
        
        .btn-outline-primary {
            color: var(--primary-color);
            border-color: var(--primary-color);
        }
        
        .btn-outline-primary:hover {
            background-color: var(--primary-color);
            border-color: var(--primary-color);
            color: white;
        }
        
        .alert {
            border-radius: 6px;
            border: 1px solid transparent;
            padding: 1rem;
            margin-bottom: 1rem;
        }
        
        .alert-success {
            background-color: rgba(76, 201, 240, 0.1);
            border-color: rgba(76, 201, 240, 0.2);
            color: #0c5460;
        }
        
        .alert-info {
            background-color: rgba(67, 97, 238, 0.1);
            border-color: rgba(67, 97, 238, 0.2);
            color: #0c5460;
        }
        
        .alert-warning {
            background-color: rgba(247, 37, 133, 0.1);
            border-color: rgba(247, 37, 133, 0.2);
            color: #856404;
        }
        
        .alert-danger {
            background-color: rgba(220, 53, 69, 0.1);
            border-color: rgba(220, 53, 69, 0.2);
            color: #721c24;
        }
        
        hr {
            border: 0;
            border-top: 1px solid var(--border-color);
            margin: 1.5rem 0;
        }
        
        .text-muted {
            color: var(--text-muted) !important;
        }
        
        .text-success {
            color: var(--success-color) !important;
        }
        
        .text-warning {
            color: var(--warning-color) !important;
        }
        
        .text-primary {
            color: var(--primary-color) !important;
        }
        
        .table {
            width: 100%;
            margin-bottom: 1rem;
            color: var(--text-color);
        }
        
        .table th {
            background-color: var(--light-gray);
            font-weight: 600;
        }
        
        .table-striped tbody tr:nth-of-type(odd) {
            background-color: rgba(0, 0, 0, 0.02);
        }
        
        .table-bordered {
            border: 1px solid var(--border-color);
        }
        
        .table-bordered th,
        .table-bordered td {
            border: 1px solid var(--border-color);
        } 
        .puzzle-solved .puzzle-tile {
            animation: celebrate 0.5s ease;
        }
        
        @keyframes celebrate {
            0% { transform: scale(1) rotate(0deg); }
            25% { transform: scale(1.1) rotate(5deg); }
            50% { transform: scale(1.05) rotate(-5deg); }
            75% { transform: scale(1.1) rotate(5deg); }
            100% { transform: scale(1) rotate(0deg); }
        }
        
        .solver-controls {
            display: flex;
            align-items: center;
            gap: 1rem;
            margin: 1rem 0;
            flex-wrap: wrap;
        }
        
        .control-group {
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }
        
        .control-label {
            font-weight: 600;
            color: var(--text-color);
        }
        
        .solver-visualization {
            margin: 1.5rem 0;
            background-color: var(--light-gray);
            border-radius: 8px;
            padding: 1.5rem;
            border: 1px solid var(--border-color);
        }