css如何实现随鼠标移动div渐变色效果

<div class="art">
<div class="box lvl6">
<div class="box lvl5">
<div class="box lvl4">
<div class="box lvl3">
<div class="box lvl3">
<div class="box lvl3">
<div class="box lvl2">
<div class="box lvl2">
<div class="box lvl2">
<div class="box lvl2">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
<div class="box lvl1">
</div>
</div>
</div>
</div>
</div>
</div>
</div>

body{
background:#ecf0f1;
}</p> <p>.art{
width:400px;
margin:0px auto;
}</p> <p>.box{
border-radius:30%;
width:200px;
height:200px;
border:1px solid #2c3e50;
padding:10px;
opacity:0.97;
}</p> <p>.lvl1{
text-align:center;
line-height:200px;
}</p> <p>.lvl1:hover{ background:#f1c40f;}
.lvl2:hover{ background:#f39c12;}
.lvl3:hover{ background:#e67e22;}
.lvl4:hover{ background:#d35400;}
.lvl5:hover{ background:#e74c3c;}
.lvl6:hover{ background:#c0392b;}