利用 background的linear-gradient的属性实现
//从下往上
background: linear-gradient(to top, #e0efff 0%, #a6d1ff 100%);
//从左往右
background: linear-gradient(to right, #f3f9ff 0%, #cae3ff 100%);
//从下往上
background: linear-gradient(to top, #e0efff 0%, #a6d1ff 100%);
//从左往右
background: linear-gradient(to right, #f3f9ff 0%, #cae3ff 100%);