.box{ 子级
position: relative;
width: 300px;
height: 400px;
display: flex;
justify-content: center;
align-content: center;
background: #1B6D85;
}
.box::before{
content: "";
position: absolute;
top: -2px;
right: -2px;
bottom: -2px;
left: -2px;
background: white;
z-index: -1;
}
.box::after{
content: "";
position: absolute;
top: -2px;
right: -2px;
bottom: -2px;
left: -2px;
background: white;
z-index: -2;
filter: blur(60px);
}
.box::before,
.box::after{
background: linear-gradient(235deg,#89ff00,#1b6d85,#00bcd4);
}
.content{ 父级
color: white;
padding: 20px;
}