* {
    box-sizing: border-box;
}

html, body {
    height: 100%;
    width: 100%;
    margin: 0;
    padding: 0;
}

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

#top-header {
    width: 100%;
    background-image: linear-gradient(to right, white, #9df);
    color: white;
    height: 1.5em;
    display: none;
    font-family: sans-serif;
    padding: 0.2em;
}

@media only screen and (max-width: 900px) {
    #mapDiv {
        top: 1.5em;
    }

    #top-header {
        display: block;
    }
}