sumup/themes/basic/static/css/style.css

.container {
    margin: 0 auto;
    width: 80%;
}
nav, footer {
    background-color: #333;
    color: #fff;
    text-align: center;
}
nav {
    display: flex;
    flex-direction: column;
}
footer li, footer ul {
    display: inline;
    margin: 0;
    padding: 0;
}
footer li::after {
    content: " | "
}
nav > a, footer a {
    flex: 1;
    text-align: center;
    text-decoration: none;
    color: #fff;
}

@media only screen and (min-width: 768px) {
    nav { flex-direction: row; }
}

.project-container { display: flex; }

.project-container .project-list { width: 20%; }

.project-container .project { flex: 1; }
/* might do the same with present(ation) */

.oss {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
}

.oss article {
    border: 1px solid #ddd;
    box-shadow: 3px 3px 3px #ddd;
    margin: 0.5%;
    padding: 0.5%;
    width: 30%;
}