css 径向渐变

.example {
        width: 150px;
        height: 80px;
        background: -webkit-radial-gradient(red, green, blue); /* Safari 5.1 - 6.0 */
        background: -o-radial-gradient(red, green, blue); /* Opera 11.6 - 12.0 */
        background: -moz-radial-gradient(red, green, blue); /* Firefox 3.6 - 15 */
        background: radial-gradient(red, green, blue); /* 标准的语法 */
    }  

.example {
        width: 150px;
        height: 80px;
        background: -webkit-radial-gradient(red 5%, green 15%, blue 60%); /* Safari 5.1 - 6.0 */
        background: -o-radial-gradient(red 5%, green 15%, blue 60%); /* Opera 11.6 - 12.0 */
        background: -moz-radial-gradient(red 5%, green 15%, blue 60%); /* Firefox 3.6 - 15 */
        background: radial-gradient(red 5%, green 15%, blue 60%); /* 标准的语法 */
    }  

circle 或 ellipse

.example {
        width: 150px;
        height: 80px;
        background: -webkit-radial-gradient(circle, red, yellow, green); /* Safari 5.1 - 6.0 */
        background: -o-radial-gradient(circle, red, yellow, green); /* Opera 11.6 - 12.0 */
        background: -moz-radial-gradient(circle, red, yellow, green); /* Firefox 3.6 - 15 */
        background: radial-gradient(circle, red, yellow, green); /* 标准的语法 */
    }  

　　

来源：https://www.cnblogs.com/chenyi4/p/11417554.html