JSFiddle - React, Tailwind, and code Playground

HTML

<div class="background">
    
    <div class="to_top">
        <div class="title"><a href="#">to top</a></div>
    </div>
    
</div>

CSS

.background {
    background: black;
    height: 300px;
}

.to_top {
    display: table;
    position: relative;            
    width: 70px;
    height: 70px;
    background: #ffdd00;
    border: 1px solid #fff;
    border-radius: 50%;
    -o-border-radius: 50%;
    -moz-border-radius: 50%;
    -webkit-border-radius: 50%;
}

.to_top .title {
    display: table-cell;
    width: 69px;
    height: 69px;
    border: 1px solid #BFBFBF;
    border-radius: 50%;
    -o-border-radius: 50%;
    -moz-border-radius: 50%;
    -webkit-border-radius: 50%;
    font: 18px bold sans-serif;
    text-align: center;
    vertical-align: middle;
}

.to_top .title a {
    display: block;
    color: #5c5c5c;
    text-decoration: none;
    width: 100%;
    height: 100%;
    line-height: 70px;
}

.to_top .title a:before{
    content: "";
    display: table-cell;
    position: absolute;
    width: 0px;
    height: 0px;
    top: 15px;
    left: 25px;
    border-bottom: 10px solid #5c5c5c;
    border-left: 10px solid transparent;
    border-right: 10px solid transparent;
}

.to_top:hover .title a {
    color: #000;
}

.to_top:hover .title a:before{
border-bottom: 10px solid #000;
}