一些奇怪的知识

要做一个如图所示的阴影效果：

彩色阴影的制作过程：

.square{
    position: absolute;
     300px;
    height: 300px;   
    background: linear-gradient(to bottom,#ff3190,#e74ff7,#a755ff,#605fff);
    border-radius: 50%;
}
.square::before{
    position: absolute;
    content: "";
     300px;
    height: 300px;   
    background: linear-gradient(to bottom,#ff3190,#e74ff7,#a755ff,#605fff);
    border-radius: 50%;
    filter: blur(35px) brightness(80%) opacity(.8);

}