style.css

* {
    box-sizing: border-box;
}

#labyrinthe {
    display: flex;
    flex-wrap: wrap;
}

.case {
    background-color: black;
    width: 100px;
    height: 100px;
}

.start{
    background-image: url("https://cdns-images.dzcdn.net/images/artist/f81e9d3704b453c60ba75289954826cc/500x500.jpg");
    background-repeat: no-repeat;
    background-size: 100%;
}

.exit{
    background-image: url("https://previews.123rf.com/images/memoangeles/memoangeles1606/memoangeles160600008/59922290-maman-inquiet-clipart-illustration-avec-des-d%C3%A9grad%C3%A9s-simples-maman-et-la-sueur-sur-des-calques.jpg");
    background-repeat: no-repeat;
    background-size: 100%;
}

p{
    color: blue;
    font-weight: bold;
    font-size: 2rem;
}

div {
    display: flex;
    justify-content: center;
    align-items: center;
}

img{
    width: 98px;
}