css如何做一个正方形缺少一角效果

css如何做一个正方形缺少一角效果，下面编程教程网小编给大家详细介绍一下具体实现代码！

具体实现代码：

.box {
  position: relative;
  width: 200px;
  height: 200px;
  background-image: linear-gradient(90deg, #333333, #666666, #999999);
  overflow: hidden;
}
.box::before {
  position: absolute;
  content: "";
  width: 100px;
  height: 100px;
  right: -50px;
  top: -50px;
  z-index: 100;
  background-color: #ffffff;
  transform: rotateZ(45deg);
}