如何使用CSS缩进多个级别的select optgroup？

<style>
    .select-wrapper {
        position: relative;
    }
    
    .optgroup-level-1 {
        padding-left: 10px;
    }
    
    .optgroup-level-2 {
        padding-left: 20px;
    }
    
    /* 更多级别的缩进样式可以根据需要添加 */
    
    .select-wrapper optgroup {
        position: absolute;
        left: 0;
    }
</style>

<div class="select-wrapper">
    <select>
        <optgroup label="Level 1" class="optgroup-level-1">
            <option>Option 1</option>
            <option>Option 2</option>
        </optgroup>
        <optgroup label="Level 2" class="optgroup-level-2">
            <option>Option 3</option>
            <option>Option 4</option>
        </optgroup>
    </select>
</div>