site.css

#map {
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
}

.leaflet-marker-icon, .leaflet-marker-shadow {
    transition: transform 0.25s ease;
    -webkit-transition: transform 0.25s ease;
    -o-transition: transform 0.25s ease;
    -moz-transition: transform 0.25s ease;
}

#forkongithub a {
    background:#000;
    color:#fff;
    text-decoration:none;
    font-family:arial,sans-serif;
    text-align:center;
    font-weight:bold;
    padding:5px 40px;
    font-size:1rem;
    line-height:2rem;
    position:relative;transition:0.5s;
}

#forkongithub a:hover{
    background:#c11;
    color:#fff;
}

#forkongithub a::before,#forkongithub a::after{
    content:"";
    width:100%;
    display:block;
    position:absolute;
    top:1px;
    left:0;
    height:1px;
    background:#fff;
}

#forkongithub a::after{
    bottom:1px;
    top:auto;

}

@media screen and (min-width:800px){
    #forkongithub{
        position:fixed;
        display:block;
        top:0;
        right:0;
        width:200px;
        overflow:hidden;
        height:200px;
        z-index:9999;
    }
    #forkongithub a{
        width:200px;
        position:absolute;
        top:60px;
        right:-60px;
        transform:rotate(45deg);
        -webkit-transform:rotate(45deg);
        -ms-transform:rotate(45deg);
        -moz-transform:rotate(45deg);
        -o-transform:rotate(45deg);
        box-shadow:4px 4px 10px rgba(0,0,0,0.8);
    }
}