CSS实现半边边框（只有边框的部分可见）

<div class="part box">
	<h1>内容</h1>
	<!-- 绘出下面两个对角边框-->
	<div class="part-footer"></div>
</div>

• 主要代码

.box {
	width: 100px;
	height: 100px;
}
.part {
	position: relative;
	&::before {
		position: absolute;
		top: 0;
		left: 0;
		content: '';
		width: 20px;
		height: 20px;
		border-left: 4px solid #4381ad;
		border-top: 4px solid #4381ad;
	}
	&::after {
		position: absolute;
		top: 0;
		right: 0;
		content: '';
		width: 20px;
		height: 20px;
		border-right: 4px solid #4381ad;
		border-top: 4px solid #4381ad;
	}
	.part-footer {
		position: absolute;
		bottom: 0;
		left: 0;
		width: 100%;
		&::before {
			position: absolute;
			bottom: 0;
			left: 0;
			content: '';
			width: 20px;
			height: 20px;
			border-left: 4px solid #4381ad;
			border-bottom: 4px solid #4381ad;
		}
		&::after {
			position: absolute;
			right: 0;
			bottom: 0;
			content: '';
			width: 20px;
			height: 20px;
			border-right: 4px solid #4381ad;
			border-bottom: 4px solid #4381ad;
		}
	}
}