.row {
    display: flex;
    margin-bottom: 3em;
}

.column {
    flex: 50%;
}

.flex {
    display: flex;
    justify-content: space-evenly;
    flex-wrap: wrap;
}

#controls {
    justify-content: space-between;
}

#controls > div {
    margin-bottom: 1em;
}

.flex > div {
    min-width: 400px;
}