button.back-to-top {
        width: 60px;
        height: 60px;
        position: fixed;
        z-index: 999;
        right: 20px;
        bottom: 20px;
        border: none;
        -webkit-border-radius: 30px;
        -moz-border-radius: 30px;
        border-radius: 30px;
        cursor: pointer;
        display: none;
        background: rgb(244,121,32);
    }
    
    button.back-to-top span {
    font-size: 2rem;
    }