html, body, #container /*, and all other map parent selectors*/ {
    height: 100%;
    overflow: hidden;
    width: 100%;
}

#container {
    display: flex;
    flex-flow: column;
    height: 100%;
}

#container form {
    flex: 0 1 auto;
}

#map {
    flex: 1 1 auto;
}