body {
    margin: 0;
    padding: 0;
    font-family: sans-serif;
    font-size: 16px;
}
#site {
    display: grid;
    grid-template-columns: 1fr 3fr;
    grid-template-areas:
                    "header header"
                    "nav article"
                    "footer footer";
}

header {
    background-color: #2c3e50;
    grid-area: header;
}
header h1 {
    text-align: center;
    font-size: 25px;
    color: #ecf0f1;
}
nav {
    background-color: #7f8c8d;
    grid-area: nav;
}
nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
}
nav li {
    text-align: center;
    padding: 30px;
}
nav a {
    color: #000;
    text-decoration: none;
    font-size: 18px;
    font-weight: bold;
    transition: 0.5s;
}
nav a:hover {
    color: #fff;
}
article {
    background-color: #ecf0f1;
    grid-area: article;
    padding: 25px;
    /* column-count: 3; */
    column-width: 200px;        /* adapte le nombre de colonnes en fonction de la largeur de l'écran*/
    column-gap: 30px;
    column-rule: 1px dashed #2c3e50;
}
article h2 {
    column-span: all;
    text-align: center;
    font-size: 40px;
    color: #2c3e50;
}
article p {
    text-align: justify;
    color: #333;
}
article p:nth-child(2) {
    margin: 0;
    padding: 0;
}
article p:nth-child(2)::first-letter {
    font-size: 30px;
}
footer {
    background-color: #2c3e50;
    grid-area: footer;
}
footer p {
    text-align: center;
    color: #ccc;
    font-style: italic;
}



@media screen and (max-width: 850px) {
    #site {
        grid-template-columns: 1fr;
        grid-template-areas:
                        "header"
                        "nav"
                        "article"
                        "footer";
    }
    nav ul {
        display: flex;                  /* Mise en ligne */
        justify-content: center;        /* centrer sur l'axe principal*/
    }
    article {
        column-count: 1;
    }
}