body {
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
            background-color: #f0f2f5;
            color: #333;
            display: flex;
            justify-content: center;
            align-items: center;
            min-height: 100vh;
            margin: 0;
        }
        .quiz-container {
            background: #ffffff;
            width: 100%;
            max-width: 500px;
            border-radius: 10px;
            box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
            padding: 25px 30px;
            box-sizing: border-box;
        }
        h1 {
            text-align: center;
            margin-top: 0;
            color: #007bff;
        }
        #question {
            font-size: 1.25rem;
            font-weight: 600;
            margin-bottom: 20px;
        }
        #answer-buttons {
            display: flex;
            flex-direction: column;
            gap: 10px;
        }
        .btn {
            width: 100%;
            padding: 12px;
            font-size: 1rem;
            text-align: left;
            border: 2px solid #ddd;
            border-radius: 8px;
            background-color: #fdfdfd;
            color: #333;
            cursor: pointer;
            transition: background-color 0.2s, border-color 0.2s;
        }
        .btn:hover:not(:disabled) {
            background-color: #f0f0f0;
            border-color: #bbb;
        }
        .btn:disabled {
            cursor: not-allowed;
            opacity: 0.7;
        }
        .btn.correct {
            background-color: #d4edda;
            border-color: #28a745;
            color: #155724;
            font-weight: 600;
        }
        .btn.incorrect {
            background-color: #f8d7da;
            border-color: #dc3545;
            color: #721c24;
            font-weight: 600;
        }
        #next-btn {
            width: 100%;
            padding: 12px;
            font-size: 1.1rem;
            font-weight: 600;
            border: none;
            border-radius: 8px;
            background-color: #007bff;
            color: white;
            cursor: pointer;
            margin-top: 20px;
            transition: background-color 0.2s;
            display: none; 
        }
        #next-btn:hover {
            background-color: #0056b3;
        }