style.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Times New Roman';
}

nav {
    border: 2px solid red;
    height: auto;
    width: auto;
    padding: 1rem;
    text-align: center;
    background-color: yellow;
}

a {
    font-size: 1.5rem;
    margin: 1rem;
    text-decoration: none;
    color: blue;
}

a:hover {
    text-decoration: underline;
}

hr {
    margin: 1rem 0rem;
}

div {
    border: 2px solid red;
    height: auto;
    width: 100%;
    background-color: yellow;
    color: blue;
    font-size: 1.3rem;
    padding: 1rem;
}

h1 {
    text-align: center;
}

footer {
    height: auto;
    width: auto;
    padding: 0rem 0rem 1rem 0rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

#btn {
    margin: 0;
}

button {
    border: 2px solid red;
    height: auto;
    width: auto;
    background-color: yellow;
    color: blue;
    font-size: 1.5rem;
    font-weight: bold;
    padding: 1rem;
    cursor: pointer;
}

#copyright {
    text-decoration: none;
    text-align: center;
    font-size: 1rem;
    margin: 0;
}