首先看效果圖
再看css是如何實現
<!DOCTYPE html>
<html><head><meta charset="utf-8"><title></title><style>.main {background-color: aqua;display: block;width: 300px;padding: 0px 32px;box-sizing: border-box;}/* 新增的子元素樣式 */.main-inner {/* padding: 0 16px; */border-bottom: 1px solid black;height: 100%;height: 300px;}</style></head><body><div><div class="main"><!-- 新增子元素 --><div class="main-inner">1111</div></div></div></body>
</html>
