简单的demo，点击切换背景颜色切换，附上代码。
.html文件
class='red' id=box>美美哒！...........
.css文件
.red{ width:100px; height:100px; background-color:red; border-radius:0 70px 0 60px ; transition-duration:1s;}.yellow{ width:150px; height:150px; border-radius:80px 0 100px 0; transition-duration:1s; background-color:yellow;}
.js文件
window.onload = function(){ var box = document.getelementbyid('box'); box.onclick = toyellow;};function tored(){ this.classname ='red'; this.onclick = toyellow;}function toyellow(){ this.classname ='yellow'; this.onclick = tored;}