:root {
            --primary-color: #2c3e50;
            --secondary-color: #3498db;
            --background-color: #ecf0f1;
            --text-color: #333;
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
        }

        body {
            background-color: var(--background-color);
            color: var(--text-color);
            line-height: 1.6;
            display: flex;
            justify-content: center;
            padding: 2rem;
        }

        .container {
            background-color: white;
            border-radius: 10px;
            box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
            padding: 2rem;
            width: 100%;
            max-width: 800px;
        }

        h1 {
            color: var(--primary-color);
            text-align: center;
            margin-bottom: 1.5rem;
        }

        .controls {
            display: flex;
            gap: 1rem;
            margin-bottom: 1.5rem;
        }

        .controls input, 
        .controls button {
            padding: 0.5rem;
            border: 1px solid var(--secondary-color);
            border-radius: 5px;
        }

        .controls button {
            background-color: var(--secondary-color);
            color: white;
            cursor: pointer;
            transition: background-color 0.3s ease;
        }

        .controls button:hover {
            background-color: #2980b9;
        }

        #problems {
            display: grid;
            gap: 1rem;
        }

        .problem {
            background-color: #f7f9fa;
            border-radius: 5px;
            padding: 1rem;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

        .problem-math {
            font-size: 1.1rem;
        }

        .problem-answer {
            color: var(--secondary-color);
            cursor: pointer;
            user-select: none;
        }

        .problem-answer.visible {
            color: var(--text-color);
        }

        #export-json {
            margin-top: 1rem;
            background-color: var(--primary-color);
        }
        
        .back-to-dashboard {
            position: fixed;
            bottom: 20px;
            right: 20px;
            width: 40px;
            height: 40px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            text-decoration: none;
            transition: all 0.3s ease;
            z-index: 1000;
            background-color: var(--primary-color);
            color: white;
            box-shadow: 0 4px 6px rgba(0, 0, 0, 0.2);
        }
        
        .back-to-dashboard:hover {
            transform: translateY(-2px);
            box-shadow: 0 6px 8px rgba(0, 0, 0, 0.3);
            background-color: var(--secondary-color);
        }
        
        .back-to-dashboard svg {
            width: 20px;
            height: 20px;
            stroke: currentColor;
        }