html, body {
    height: 100%;
    margin: 0; padding: 0;
}

body {
    background-image: url("fond_accueil.jpg");
    background-attachment: fixed;
    background-size: 100%;
    /*background-color: rgb(50 50 50);*/
    display : table;
    width: 100%;
    margin: 0px;
    padding: 0px;
}

li, a{
    font-size: 16px;
    color: #edf0f1;
    text-decoration: none;
}

header{
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 30px 10%;

    background-color: #24252a;

}

.logo{
    cursor: pointer;
}

.nav_links{
    list-style: none;
}

.nav_links li{
    display: inline-block;
    padding: 0px 20px;
}

.nav_links li a{
    transition: all 0.3s ease 0s;
}

.nav_links li a:hover{
    color: #0088a9;
}

p{
    font-size: 25pt;
    font-family:  'Playfair Display', Arial;
    font-style: italic
}

#en_cours{
    background-color: rgb(117 190 218 / 65%);
    text-align: center;
    padding: 30px;
}

#grand_logo{
    width: 500px
}

.presentation{
    background-color: rgb(250 250 250 / 65%);
    padding: 30px;
    margin: 30px 0 30px 0 ;
}

#photo_athena{
    float: left;
    border-radius: 15%;
    shape-outside: margin-box;
    margin: 0 20px 5px 0;
    width: 500px;
}

.presentation::after{
    content: "";
    display: block;
    clear: both;
}

footer{
    background-color: rgb(50, 90, 50);
    display : table-row;
    height: 150px; /* à titre d'exemple */

    text-align: center;
    color: rgb(255, 255, 255);
    font-size: 15pt;
}