* {
    margin: 0;
    padding: 0;
}

details.main {
    margin: 1em;
    background-color: red;
}

details.main > summary {
    font-weight: bold;
}

details.pronounce {
    background-color: yellow;
}

details.syntax {
    background-color: blue;
}

details.synonym {
    background-color: purple;
}

details.antonym {
    background-color: green;
}