web-tp-site/styles/main.css

* {
    box-sizing: border-box;
}

body {
    font-family: Arial;
    margin: 0;
}


/* HEADER --------------------------------------------*/

.header {
    position: sticky;
}

.header .title {
    background-image: linear-gradient(to right, #ebebeb, cadetblue);
    text-align: center;
    padding: 60px;
    color: #ebebeb;
}

.nav-bar a:link { color: white; }
.nav-bar a:visited { color: white; }
.nav-bar a:hover {
    color: #555;
    background-color: #ebebeb;
    border: 10px solid #ebebeb;
    border-radius: 25px;
    font-size: 20px;
}


.nav-bar {
    display: flex;
    justify-content: space-between;
    padding: 5px;
    align-items: baseline;
    background-color: #555;
}

.nav-bar a {
    padding: 5px 20px;
    margin: 0 10px 0 10px;
    text-align: center;
    text-decoration: none;
    border-radius: 25%;
    transition:
        border 300ms,
        font-size 300ms,
        background-color 300ms,
        color 300ms;
}

.nav-left {
    display: flex;
    justify-content: flex-start;
    align-items: baseline;
}

.nav-right {
    display: flex;
    justify-content: flex-end;
    align-items: baseline;
}

/* MAIN CONTENT --------------------------------------------*/

.main-content {
    display: flex;
    flex-wrap: wrap;
}

.side {
    flex: 20%;
    background-color: #f1f1f1;
    padding: 20px;
}

.main {
    flex: 80%;
    background-color: #ebebeb;
    padding: 20px;
}

article {
    border-bottom: 1px solid #555;
}

.title-link {
    text-decoration: none;
    color: black;
}


/* RESPONSIVE -----------------------------------------------------*/

@media screen and (max-width: 700px) {
    .main-content, .nav-bar {
        flex-direction: column;
    }
}