> For the complete documentation index, see [llms.txt](https://mm.ricky.moe/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mm.ricky.moe/interview/inverview-record/tou-tiao-mian-jing/bi-shi/css-hua-zheng-fang-xing.md).

# CSS 画正方形

## vw 单位

```css
.placeholder {
    width: 50vw;
    height: 50vw;
}
```

## padding-bottom

```css
.placeholder{
    width: 50%;
    padding-bottom: 50%;/* padding百分比相对父元素宽度计算 */
    height: 0; //避免被内容撑开多余的高度
}
```