body {
        font-family: Arial, sans-serif;
    }
    .tab {
        display: none;
    }
    .tab div {
        margin-bottom: 15px;
    }
    .tab label {
        display: block;
        font-weight: bold;
        margin-bottom: 5px;
    }
    .tab input, .tab select {
        display: block;
        width: 100%;
        padding: 8px;
        border: 1px solid #ccc;
        border-radius: 4px;
    }
    .invalid {
        border: 2px solid red;
    }
    .step {
        display: inline-block;
        padding: 10px;
        margin: 5px;
        background: #ddd;
        border-radius: 50%;
    }
    .active {
        background: #4CAF50;
        color: white;
    }
    .buttons {
        margin-top: 20px;
    }
    #prevBtn {
        display: none;
    }