body {
    font-family: Arial, Helvetica, sans-serif;
    font-size: 16px;
    line-height: 1.6;
}

h1, h2, h3 {
    font-family: Arial, Helvetica, sans-serif;
}

h1 {
    text-align: center;
}

main img {
    display: block;
    margin-left: auto;
    margin-right: auto;
}

#sommaire {
    position: fixed;
    top: 0;
    left: 0;
    width: 20%;
    height: 100vh;
    padding: 20px;
    box-sizing: border-box;
    background-color: #f5f5f5;
    overflow-y: auto;
}

#sommaire a {
    display: block;
    margin-bottom: 10px;
}

main {
   margin-left: 20%;
    padding: 20px;
}