hover box-shadow with no repaint

by jorgeluis

HTML

<p>Animate box-shadow without repaint</p>

<button type="button">Hover</button>
<button type="button">Over</button>
<button type="button">Us</button>

CSS

/* thanks to http://tobiasahlin.com/demo/animate-box-shadow/ */

body {
    background: #eadda9;
}
button {
    display: inline-block;
    position: relative;
    top: 0;
    background-color: rgb(0,100,200);
    color: #fff;
    width: 150px;
    height: 150px;
    margin: 10px;
    border: 0;
    border-radius: 5px;
    font-size: 1em;
    
    box-shadow: 0 2px 2px rgba(100,30,145,0.6);
    position: relative;
    -webkit-transform: translateY(0);
    -webkit-transition: all 0.6s cubic-bezier(0.165, 0.84, 0.44, 1);
    transition: all 0.6s cubic-bezier(0.165, 0.84, 0.44, 1);
}

button:after {
    content: "";
    border-radius: 5px;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    box-shadow: -2px 2px 5px rgba(100,80,145,0.6);
    opacity: 0;
    -webkit-transition: all 0.6s cubic-bezier(0.165, 0.84, 0.44, 1);
    transition: all 0.6s cubic-bezier(0.165, 0.84, 0.44, 1);
}
button:hover {
    color: #fff;
    background-color: rgb(10,140,200);
    top: -4px;
}
button:hover:after {
    opacity: 1;
    box-shadow: -12px 12px 20px rgba(100,30,145,0.3);
}