利用径向渐变实现 不规则渐变阴影

gistfile1.css

.top-shadow {
  width: 200px;
  height: 200px;
}

.top-shadow:after {
  content: "";
  width: 100%;
  height: 8px;
  display: block;
  background-image: -webkit-radial-gradient(center top,ellipse farthest-side , rgba(0, 0, 0, 0.3) , transparent);
  background-repeat: no-repeat;
}