* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            -webkit-user-select: none;
            user-select: none;
        }

        body {
            font-family: 'Comic Sans MS', cursive, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            display: flex;
            justify-content: center;
            align-items: center;
            padding: 20px;
        }

        .container {
            background: white;
            border-radius: 30px;
            padding: 40px;
            max-width: 800px;
            width: 100%;
            box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
        }

        h1 {
            text-align: center;
            color: #667eea;
            font-size: 2.5em;
            margin-bottom: 10px;
            text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.1);
        }

        .mode-selector {
            display: flex;
            gap: 10px;
            justify-content: center;
            margin-bottom: 20px;
        }

        .mode-btn {
            background: #e0e0e0;
            color: #666;
            border: none;
            padding: 10px 25px;
            font-size: 1.1em;
            font-weight: bold;
            border-radius: 15px;
            cursor: pointer;
            transition: all 0.3s;
        }

        .mode-btn.active {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
        }

        .score-board {
            display: flex;
            justify-content: space-around;
            margin-bottom: 30px;
            background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
            padding: 15px;
            border-radius: 20px;
            color: white;
        }

        .score-item {
            text-align: center;
            font-size: 1.2em;
            font-weight: bold;
        }

        .game-area {
            background: linear-gradient(135deg, #ffecd2 0%, #fcb69f 100%);
            border-radius: 20px;
            padding: 30px;
            margin-bottom: 20px;
            min-height: 400px;
        }

        .number-bond-display {
            display: flex;
            flex-direction: column;
            align-items: center;
            margin-bottom: 30px;
        }

        .addition-mode .number-bond-display {
            flex-direction: column;
        }

        .subtraction-mode .number-bond-display {
            flex-direction: row;
            justify-content: center;
            align-items: center;
            gap: 20px;
        }

        .whole-number {
            background: linear-gradient(135deg, #fa709a 0%, #fee140 100%);
            width: 120px;
            height: 120px;
            border-radius: 50%;
            display: flex;
            justify-content: center;
            align-items: center;
            font-size: 3em;
            font-weight: bold;
            color: white;
            text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
            box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2);
            margin-bottom: 20px;
            animation: pulse 2s infinite;
        }

        .subtraction-mode .whole-number {
            margin-bottom: 0;
        }

        @keyframes pulse {

            0%,
            100% {
                transform: scale(1);
            }

            50% {
                transform: scale(1.05);
            }
        }

        .parts-container {
            display: flex;
            gap: 40px;
            margin-top: 20px;
        }

        .subtraction-mode .parts-container {
            margin-top: 0;
            gap: 20px;
        }

        .part-slot {
            background: white;
            width: 100px;
            height: 100px;
            border-radius: 20px;
            border: 4px dashed #ccc;
            display: flex;
            justify-content: center;
            align-items: center;
            font-size: 2.5em;
            font-weight: bold;
            color: #999;
            transition: all 0.3s;
        }

        .part-slot.filled {
            border-color: #4CAF50;
            background: linear-gradient(135deg, #a8edea 0%, #fed6e3 100%);
            color: #333;
        }

        .operator {
            font-size: 3em;
            font-weight: bold;
            color: #555;
        }

        .draggable-numbers {
            display: flex;
            flex-wrap: wrap;
            gap: 15px;
            justify-content: center;
            margin-top: 40px;
        }

        .number-tile {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            width: 80px;
            height: 80px;
            border-radius: 15px;
            display: flex;
            justify-content: center;
            align-items: center;
            font-size: 2em;
            font-weight: bold;
            color: white;
            cursor: grab;
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
            transition: all 0.2s;
            touch-action: none;
            position: relative;
        }

        .number-tile:hover {
            transform: scale(1.05);
        }

        .number-tile:active {
            cursor: grabbing;
            transform: scale(1.1);
            box-shadow: 0 8px 25px rgba(0, 0, 0, 0.4);
        }

        .number-tile.dragging {
            opacity: 0.5;
            z-index: 1000;
        }

        .number-tile.used {
            opacity: 0.3;
            cursor: not-allowed;
            pointer-events: none;
        }

        .part-slot.drag-over {
            border-color: #667eea;
            background: #e3f2fd;
            transform: scale(1.05);
        }

        .feedback {
            text-align: center;
            font-size: 1.8em;
            font-weight: bold;
            margin: 20px 0;
            min-height: 50px;
        }

        .feedback.success {
            color: #4CAF50;
            animation: bounce 0.5s;
        }

        .feedback.error {
            color: #f44336;
            animation: shake 0.5s;
        }

        @keyframes bounce {

            0%,
            100% {
                transform: translateY(0);
            }

            50% {
                transform: translateY(-10px);
            }
        }

        @keyframes shake {

            0%,
            100% {
                transform: translateX(0);
            }

            25% {
                transform: translateX(-10px);
            }

            75% {
                transform: translateX(10px);
            }
        }

        .buttons {
            display: flex;
            gap: 15px;
            justify-content: center;
            flex-wrap: wrap;
        }

        button {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            border: none;
            padding: 15px 30px;
            font-size: 1.2em;
            font-weight: bold;
            border-radius: 15px;
            cursor: pointer;
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
            transition: all 0.3s;
        }

        button:hover {
            transform: translateY(-2px);
            box-shadow: 0 6px 20px rgba(0, 0, 0, 0.3);
        }

        button:active {
            transform: translateY(0);
        }

        .instruction {
            text-align: center;
            font-size: 1.3em;
            color: #555;
            margin-bottom: 20px;
            font-weight: bold;
        }

        @media (max-width: 600px) {
            .container {
                padding: 20px;
            }

            h1 {
                font-size: 2em;
            }

            .whole-number {
                width: 100px;
                height: 100px;
                font-size: 2.5em;
            }

            .part-slot {
                width: 80px;
                height: 80px;
                font-size: 2em;
            }

            .number-tile {
                width: 70px;
                height: 70px;
                font-size: 1.8em;
            }
        }