html,
body {
    margin: 0;
    padding: 0;
}

body {
    height: 100vh;
    width: 100vw;
}
* {
    box-sizing: border-box;
}
div#map {
    height: 100%;
    width: 100%;

    /* example padding, font-size, background, etc */
    padding: 10px;
    font-size: 20px;
    background-color: lightskyblue;
}