Edit on
<body>
  <button>Fade Out</button>
</body>    
body > button {
    background: #428BCA;
    color: #fff;
    font-family: Sans-serif;
    font-size: 20px;
    height: 60px;
    width: 150px;
    line-height: 60px;
    margin: 25px 25px;
    text-align: center;
    border: 0;
    transition: all 0.3s ease 0s;
}

 button {
  opacity: 1;
}

button:hover {
  opacity: 0.75;
}
Rerun