style.css

header {
    text-align: center;
    text-decoration: none;
    padding: 10px;
    background-image: url(https://images.fineartamerica.com/images-medium-large-5/3-chlamydomonas-sem-aaron-j-bell.jpg);
    background-position: center;
    border-radius: 50px;
    font-family: 'Lato', sans-serif;
    font-size: large;
    color: white;
}

header h1 {
    font-size: 300%;
}

h2 {
    font-family: 'Lato', sans-serif;
    font-size: 200%;
    text-align: center;
}

/*nav*/

nav {
    background-color:seagreen;
    border-radius: 50px;
    font-size: 150%;
}

ul {
    list-style-type: none;
    text-align: center;
}

li {
    text-decoration: none;
    display: inline-block;
    align-content: center;
    font-family: 'Lato', sans-serif;
    padding: 10px;
    color: white;
}

/*javascript*/

#cy {
    height: 50%;
    width: 90%;
    position:absolute;
    background-color:seagreen;
    border-radius: 50px;
    margin-left: 70px;
}