:root {
            --primary-color: #2c7da0;
            --secondary-color: #a9d6e5;
            --accent-color: #01497c;
            --light-gray: #f8f9fa;
            --border-color: #eaeaea;
            --text-color: #333;
            --text-muted: #6c757d;
            --success-color: #28a745;
            --warning-color: #ffc107;
            --danger-color: #dc3545;
            --board-color: #1a8c4d;
            --board-line-color: #000;
            --disk-black: #000;
            --disk-white: #fff;
            --disk-black-highlight: #333;
            --disk-white-highlight: #f0f0f0;
            --valid-move-color: rgba(255, 215, 0, 0.4);
            --last-move-color: rgba(255, 165, 0, 0.6);
        }
         
        
        .page-header {
            background: linear-gradient(135deg, rgba(169, 214, 229, 0.4) 0%, rgba(44, 125, 160, 0.4) 100%);
            padding: 1.5rem 0;
            margin-bottom: 2rem;
            border-bottom: 1px solid rgba(44, 125, 160, 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;
        }
        
        .reversi-game-container {
            width: 100%;
            max-width: 700px;
            position: relative;
            margin: 0 auto;
        }
        
        .reversi-board {
            width: 100%;
            max-width: 600px;
            margin: 0 auto;
            background-color: var(--board-color);
            border-radius: 8px;
            overflow: hidden;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
            position: relative;
        }
        
        .board-grid {
            display: grid;
            grid-template-columns: repeat(8, 1fr);
            grid-template-rows: repeat(8, 1fr);
            gap: 0;
            width: 100%;
            aspect-ratio: 1 / 1;
            border: 2px solid #0a5c2f;
        }
        
        .board-cell {
            background-color: var(--board-color);
            border: 1px solid rgba(0, 0, 0, 0.3);
            position: relative;
            cursor: pointer;
            transition: background-color 0.2s;
        }
        
        .board-cell:hover {
            background-color: rgba(255, 255, 255, 0.1);
        }
        
        .board-cell.valid-move {
            background-color: var(--valid-move-color);
            cursor: pointer;
        }
        
        .board-cell.valid-move:hover {
            background-color: rgba(255, 215, 0, 0.6);
        }
        
        .board-cell.last-move {
            background-color: var(--last-move-color);
        }
        
        .disk {
            position: absolute;
            top: 10%;
            left: 10%;
            width: 80%;
            height: 80%;
            border-radius: 50%;
            box-shadow: inset 0 0 10px rgba(0, 0, 0, 0.3), 0 3px 5px rgba(0, 0, 0, 0.3);
            display: flex;
            align-items: center;
            justify-content: center;
            z-index: 2;
            transition: transform 0.3s, box-shadow 0.3s;
        }
        
        .disk.black {
            background: radial-gradient(circle at 30% 30%, var(--disk-black-highlight), var(--disk-black));
            color: white;
        }
        
        .disk.white {
            background: radial-gradient(circle at 30% 30%, var(--disk-white-highlight), var(--disk-white));
            color: #333;
        }
        
        .disk.potential {
            opacity: 0.3;
            transform: scale(0.8);
        }
        
        .disk.flipping {
            animation: flipDisk 0.6s ease-in-out;
        }
        
        @keyframes flipDisk {
            0% { transform: rotateY(0) scale(1); }
            50% { transform: rotateY(90deg) scale(1.1); }
            100% { transform: rotateY(0) scale(1); }
        }
        
        .game-info {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-top: 2rem;
            padding: 1rem 2rem;
            background-color: var(--light-gray);
            border-radius: 8px;
            border: 1px solid var(--border-color);
        }
        
        .player-info {
            display: flex;
            align-items: center;
            gap: 1rem;
        }
        
        .player-indicator {
            display: flex;
            align-items: center;
            padding: 0.5rem 1rem;
            border-radius: 6px;
            font-weight: 600;
            transition: all 0.3s;
        }
        
        .player-indicator.active {
            background-color: rgba(44, 125, 160, 0.1);
            box-shadow: 0 0 0 2px var(--primary-color);
        }
        
        .player-disk {
            width: 24px;
            height: 24px;
            border-radius: 50%;
            margin-right: 0.5rem;
        }
        
        .player-disk.black {
            background-color: var(--disk-black);
            box-shadow: inset 0 0 5px rgba(255, 255, 255, 0.3);
        }
        
        .player-disk.white {
            background-color: var(--disk-white);
            box-shadow: inset 0 0 5px rgba(0, 0, 0, 0.3);
        }
        
        .score-display {
            font-size: 1.5rem;
            font-weight: 700;
            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;
            cursor: pointer;
        }
        
        .game-btn-primary {
            background-color: var(--primary-color);
            color: white;
        }
        
        .game-btn-primary:hover {
            background-color: var(--accent-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: #218838;
            transform: translateY(-2px);
        }
        
        .game-btn-warning {
            background-color: var(--warning-color);
            color: #333;
        }
        
        .game-btn-warning:hover {
            background-color: #e0a800;
            transform: translateY(-2px);
        }
        
        .game-btn-danger {
            background-color: var(--danger-color);
            color: white;
        }
        
        .game-btn-danger:hover {
            background-color: #c82333;
            transform: translateY(-2px);
        }
        
        .game-btn-info {
            background-color: #17a2b8;
            color: white;
        }
        
        .game-btn-info:hover {
            background-color: #138496;
            transform: translateY(-2px);
        }
        
        .game-mode-selector {
            display: flex;
            background-color: var(--light-gray);
            border-radius: 6px;
            padding: 4px;
            margin-bottom: 1.5rem;
        }
        
        .mode-btn {
            flex: 1;
            text-align: center;
            padding: 0.75rem;
            border-radius: 4px;
            cursor: pointer;
            transition: all 0.3s;
            font-weight: 600;
        }
        
        .mode-btn.active {
            background-color: var(--primary-color);
            color: white;
        }
        
        .ai-difficulty {
            display: flex;
            flex-wrap: wrap;
            gap: 0.75rem;
            margin: 1.5rem 0;
        }
        
        .difficulty-btn {
            padding: 0.75rem 1.5rem;
            border-radius: 6px;
            font-weight: 600;
            background-color: white;
            border: 2px solid var(--border-color);
            transition: all 0.3s;
            cursor: pointer;
        }
        
        .difficulty-btn:hover {
            background-color: var(--light-gray);
        }
        
        .difficulty-btn.active {
            background-color: var(--primary-color);
            color: white;
            border-color: var(--primary-color);
        }
        
        .game-message {
            background: linear-gradient(135deg, rgba(40, 167, 69, 0.1) 0%, rgba(40, 167, 69, 0.3) 100%);
            border: 2px solid var(--success-color);
            border-radius: 8px;
            padding: 1.5rem;
            text-align: center;
            margin: 2rem 0;
            display: none;
        }
        
        .game-message.warning {
            background: linear-gradient(135deg, rgba(255, 193, 7, 0.1) 0%, rgba(255, 193, 7, 0.3) 100%);
            border-color: var(--warning-color);
        }
        
        .game-message.error {
            background: linear-gradient(135deg, rgba(220, 53, 69, 0.1) 0%, rgba(220, 53, 69, 0.3) 100%);
            border-color: var(--danger-color);
        }
        
        .message-title {
            font-size: 1.5rem;
            font-weight: 700;
            margin-bottom: 1rem;
        }
        
        .message-title.success {
            color: var(--success-color);
        }
        
        .message-title.warning {
            color: var(--warning-color);
        }
        
        .message-title.error {
            color: var(--danger-color);
        }
         
        .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(44, 125, 160, 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;
        }
        
        .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.black {
            border-left-color: var(--disk-black);
        }
        
        .move-item.white {
            border-left-color: var(--disk-white);
        }
        
        .game-rules {
            background-color: rgba(44, 125, 160, 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(255, 193, 7, 0.05);
            border-left: 3px solid var(--warning-color);
            padding: 1rem;
            border-radius: 0 4px 4px 0;
            margin: 1.5rem 0;
        }
        
        @media (max-width: 768px) {
            .tool-card {
                padding: 1.5rem;
            }
            
            .reversi-board {
                max-width: 100%;
            }
            
            .game-controls {
                flex-direction: column;
                align-items: center;
            }
            
            .game-btn {
                width: 100%;
                max-width: 300px;
            }
            
            .game-info {
                flex-direction: column;
                gap: 1rem;
                text-align: center;
            }
            
            .player-info {
                flex-direction: column;
                gap: 0.5rem;
            }
        }
        
        @media (max-width: 480px) {
            .reversi-board {
                max-width: 100%;
            }
            
            .board-cell {
                border-width: 0.5px;
            }
        }
        
        .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;
        }
        
        .form-control {
            border: 1px solid #ddd;
            border-radius: 6px;
            padding: 0.75rem;
            transition: all 0.3s;
        }
        
        .form-control:focus {
            border-color: var(--primary-color);
            box-shadow: 0 0 0 3px rgba(44, 125, 160, 0.15);
        }
        
        .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(--accent-color);
            border-color: var(--accent-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;
        }
        
        .btn-outline-secondary {
            color: #6c757d;
            border-color: #6c757d;
        }
        
        .btn-outline-secondary:hover {
            background-color: #6c757d;
            border-color: #6c757d;
            color: white;
        }
        
        .alert {
            border-radius: 6px;
            border: 1px solid transparent;
            padding: 1rem;
            margin-bottom: 1rem;
        }
        
        .alert-success {
            background-color: rgba(40, 167, 69, 0.1);
            border-color: rgba(40, 167, 69, 0.2);
            color: #155724;
        }
        
        .alert-info {
            background-color: rgba(23, 162, 184, 0.1);
            border-color: rgba(23, 162, 184, 0.2);
            color: #0c5460;
        }
        
        .alert-warning {
            background-color: rgba(255, 193, 7, 0.1);
            border-color: rgba(255, 193, 7, 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-danger {
            color: var(--danger-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);
        }
    
        .valid-move-indicator {
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            width: 20px;
            height: 20px;
            border-radius: 50%;
            background-color: rgba(255, 215, 0, 0.7);
            z-index: 1;
            opacity: 0;
            transition: opacity 0.3s;
        }
        
        .board-cell.valid-move .valid-move-indicator {
            opacity: 1;
        }
        
        .board-coordinates {
            position: absolute;
            color: white;
            font-weight: bold;
            font-size: 0.8rem;
            text-shadow: 1px 1px 2px rgba(0,0,0,0.7);
            pointer-events: none;
        }
        
        .coordinate-row {
            left: -25px;
            display: flex;
            align-items: center;
            justify-content: center;
            width: 20px;
        }
        
        .coordinate-col {
            top: -25px;
            display: flex;
            align-items: center;
            justify-content: center;
            height: 20px;
        }
        
        .game-statistics {
            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: 1.5rem;
            font-weight: 700;
            color: var(--primary-color);
            margin-bottom: 0.25rem;
        }
        
        .stat-label {
            color: var(--text-muted);
            font-size: 0.9rem;
        }
        
        .hint-indicator {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            border: 3px solid rgba(255, 255, 0, 0.7);
            border-radius: 4px;
            z-index: 5;
            pointer-events: none;
            animation: pulseHint 2s infinite;
        }
        
        @keyframes pulseHint {
            0% { opacity: 0.3; }
            50% { opacity: 1; }
            100% { opacity: 0.3; }
        }
        
        .sound-control {
            position: absolute;
            top: 10px;
            right: 10px;
            z-index: 10;
        }
        
        .sound-btn {
            background-color: rgba(0, 0, 0, 0.5);
            color: white;
            border: none;
            border-radius: 50%;
            width: 40px;
            height: 40px;
            display: flex;
            align-items: center;
            justify-content: center;
            cursor: pointer;
            transition: all 0.3s;
        }
        
        .sound-btn:hover {
            background-color: rgba(0, 0, 0, 0.7);
            transform: scale(1.1);
        }
        
        .thinking-indicator {
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            background-color: rgba(0, 0, 0, 0.8);
            color: white;
            padding: 10px 20px;
            border-radius: 20px;
            font-weight: bold;
            z-index: 100;
            display: none;
        }
        
        .thinking-indicator.show {
            display: block;
            animation: fadeInOut 1.5s infinite;
        }
        
        @keyframes fadeInOut {
            0%, 100% { opacity: 0.7; }
            50% { opacity: 1; }
        }
        
        .shortcut-help {
            margin-top: 1rem;
            padding: 1rem;
            background-color: rgba(23, 162, 184, 0.1);
            border-radius: 6px;
            border-left: 3px solid #17a2b8;
        }
        
        .keyboard-shortcut {
            background-color: #f8f9fa;
            border: 1px solid #dee2e6;
            border-radius: 4px;
            padding: 2px 6px;
            font-family: monospace;
            font-size: 0.9rem;
            margin: 0 2px;
        }
        
        .game-timer {
            font-size: 1.2rem;
            font-weight: bold;
            color: var(--primary-color);
            margin-left: 1rem;
        }
        
        .confetti {
            position: fixed;
            width: 10px;
            height: 10px;
            background-color: var(--primary-color);
            top: -10px;
            z-index: 9999;
            pointer-events: none;
        }