Simple css floating button

 

<style>

    .float{
        display: none;
    }

    @media only screen and (max-width: 990px) and (min-width: 400px)  {


        .float{
            display:block;
            position:fixed;
            width:40px;
            height:40px;
            /*bottom:40px;*/
            right:5px;
            top:5px;
            margin: 3px;
            /*margin-left: 90px;*/
            background-color: #e50606;
            color:#FFF;
            border-radius:5px;
            text-align:center;
            box-shadow: 2px 2px 3px #999;
        }

        .my-float{
            margin-top:11px;
        }

    }

</style>

<a href="#" class="float sidebar-toggler flex-shrink-0" >
    <i class="fa fa-bars my-float"></i>
</a>

link: https://codepen.io/androidcss/pen/yOopGp