/* HTML */
<a href="#"><button class="button-16" style="vertical-align: middle;">
<span>Download</span></button></a>

/* CSS */
.button-16 {
 display: inline-block;
 border-radius: 7px;
 border: none;
 background: #1875FF;
 color: white;
 font-family: inherit;
 text-align: center;
 font-size: 13px;
 box-shadow: 0px 14px 56px -11px #1875FF;
 width: 10em;
 padding: 1em;
 transition: all 0.4s;
 cursor: pointer;
}

.button-16 span {
 cursor: pointer;
 display: inline-block;
 position: relative;
 transition: 0.4s;
}

.button-16 span:after {
 content: 'for free';
 position: absolute;
 opacity: 0;
 top: 0;
 right: -20px;
 transition: 0.7s;
}

.button-16:hover span {
 padding-right: 3.55em;
}

.button-16:hover span:after {
 opacity: 4;
 right: 0;
}