<button>
  <span></span>
</button>

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
  font-family: "Raleway", sans-serif;
}

body {
  width: 100%;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color:#f9fafc;
}



button{  
    position: absolute;
    top: 50%;
    right: 0;
    left: 0;
    display: block;
    width: 240px;
    padding: 40px;
    margin: 0 auto;
    border: 0;
    cursor: pointer;
    border-radius: 4px;
    transform: translateY(-50%);
    box-shadow: 0 10px 20px -5px #94a6af;
    overflow: hidden;
}

button:before, button:after
{
    content: "";
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
}

button:before
{
    transform: scale(1);
    background-image: url('https://images.unsplash.com/photo-1564456553629-2fbb71cd7f6c?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=1050&q=80');
    background-size: cover;
    transition: 0.3s ease transform;
    z-index: 1;
}


button span
{
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    z-index: 3;
}



button span:before, button span:after
{
    position: absolute;
    top: 0;
    right: 0;
    left: 0;
    color: #fff;
    font-size: 30px;
    font-weight: bold;
    line-height: 1;
    text-align: center;
    padding: 25px 0;
    transition: 0.3s ease all;
}

button span:before
{
    content: "HOVER ME";
    letter-spacing: 0;
    opacity: 1;
    transform: scale(1);
}



button span:after
{
    content: "COOL !";
    letter-spacing: -10px;
    transform: scale(0);
    opacity: 0;
}

button:hover:before
{
    transform: scale(1.3);
}

button:hover span:before
{
    letter-spacing: 3px;
    opacity: 0;
    transform: scale(4);
}

button:hover span:after
{
    letter-spacing: 0;
    opacity: 1;
    transform: scale(1);
}