#grille {
    width: calc(30vmin + 12px);
    height: calc(30vmin + 12px);
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    border: solid black 1px;
}
#grille .case {
    border: solid black 1px;
    display: grid;
    place-items: center;
    height: 10vmin;
    width: 10vmin;
    margin: 1px;
}
#grille .case:hover {
    background: pink;
}

nav {
margin-top: 1em;
}