#center-container{margin:20px 0}button{padding:12px 20px;background-color:#3498db;color:#fff;border:none;border-radius:5px;cursor:pointer;font-size:16px;transition:background-color 0.3s ease}button:hover{background-color:#2980b9}button.hide{display:none}a#course-link{padding:12px 20px;background-color:#2ecc71;color:#fff;border-radius:5px;text-decoration:none;font-size:16px;transition:background-color 0.3s ease}a#course-link:hover{background-color:#27ae60}a.hide{display:none}