.btn { 
  font-weight:bold; 
  background-image: linear-gradient(#4678aa, #4d8fd0);
  border: 0;
  border-radius: 4px;
  box-shadow: rgba(0, 0, 0, .3) 0 5px 15px;
  box-sizing: border-box;
  color: #fff;
  cursor: pointer;
  margin: 5px;
  padding: 10px 15px;
  text-align: center;
  user-select: none;
  -webkit-user-select: none;
  touch-action: manipulation;
    }

input[type=radio].with-font,
input[type=checkbox].with-font {
    border: 0;
    clip: rect(0 0 0 0);
    height: 1px;
    margin: -1px;
    overflow: hidden;
    padding: 0;
    position: absolute;
    width: 1px;
}
    
input[type=radio].with-font ~ label:before,
input[type=checkbox].with-font ~ label:before {
    font-family: FontAwesome;
    display: inline-block;
    content: "\f1db";
    letter-spacing: 10px;
    font-size: 1.2em;
    color: gray;
    width: 1.4em;
}

input[type=radio].with-font:checked ~ label:before,
input[type=checkbox].with-font:checked ~ label:before  {
    content: "\f00c";
    font-size: 1.2em;
    color: darkgreen;
    letter-spacing: 5px;
}
input[type=checkbox].with-font ~ label:before {        
    content: "\f096";
}
input[type=checkbox].with-font:checked ~ label:before {
    content: "\f046";        
    color: gray;
}
input[type=radio].with-font:focus ~ label:before,
input[type=checkbox].with-font:focus ~ label:before,
input[type=radio].with-font:focus ~ label,
input[type=checkbox].with-font:focus ~ label
{                
    color: gray;
}