.nav-bar{
    text-align: center;
    border: 4px solid black;
    margin-bottom: 20px;
    background-color: black;
 }
    .nav-bar ul {
        list-style-type: none;
        padding: 0;
    }
    .nav-bar li {
        display: inline;
        margin: 0 15px;
    }
    .nav-bar a {
        text-decoration: none;
        color: white;
        font-weight: bold;
    }
    .nav-bar a:hover {
        text-decoration: underline;
    }
.courses-page {
    background-color: #f0f8ff;
    padding: 20px;
    text-align: center;
 }
 .course-list {
    margin-bottom: 30px;
 }
 .course-module {
    border: 2px solid #00008b;
    padding: 15px;
    margin-bottom: 20px;
    background-color: #e6e6fa;
 }
 .course-description {
    font-style: italic;
    margin-bottom: 10px;
 }
 .course-topics {
    margin-left: 20px;
 }