<a href="http://www.mamicode.com/#" class="a-btn">中秋节快乐啊。。。</a>

.a-btn{ display:block; position:relative; width:300px; margin:30px auto; height:40px; line-height:40px; border:2px ridge #fff; color:#fff; text-align:center; background:#343434; z-index:2;}
.a-btn:before,.a-btn:after{ content:""; display:block; width:50%; height:100%; position:absolute; top:0; z-index:1; }
.a-btn:before{left:0; }
.a-btn:after{ right:0; }
.a-btn:hover{background-color: #FFC340; }
.a-btn, .a-btn:before,.a-btn:after{transition: all 0.3s ease 0s;}
.a-btn:hover:before,.a-btn:hover:after{ width:0; background-color: #fff; }

按钮动画效果