理论上最小的单位是1px
一、最优方法：transforms属性缩放
<!DOCType html>
<html>
<head>
<meta charset="utf-8">
<style>
.hr {
width: 300px;
background-color: #000;
}
.scale-half {
height: 1px;
transform: scaleY(0.5); /* 延Y轴缩小1倍 */
transform-origin: 50% 100%; /* 改变元素变形的原点 */
}
.hr.half-px {
height: 0.5px;
}
.hr.one-px {
height: 1px;
}
</style>
</head>
<body>
<p>1px + scaleY(0.5)</p>
<div class="hr scale-half"></div>
<p>0.5px</p>
<div class="hr half-px"></div>
<p>1px</p>
<div class="hr one-px"></div>
</body>
</html>
