css加蒙板效果

.header {
	top: 0;
	width: 100%;
	height: 90px;
	position: absolute;
	z-index: 1005;
	display: flex;
	align-items: center;
	overflow: hidden;
	min-width: 1200px;
	background: hsla(0, 100%, 2%, 0.4);
	transition: transform 0.3s;
	&::before {
		content: '';
		position: absolute;
		top: 0;
		left: 0;
		right: 0;
		bottom: 0;
		z-index: -1;
		background: inherit;
		background-attachment: fixed;
		filter: blur(20px);
		margin: -30px;
	}
}