body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
}
header {
    background-color: #333;
    color: #fff;
    padding: 10px 0;
}
nav ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    text-align: center;
}
nav ul li {
    display: inline-block;
    position: relative;
    margin-right: 20px;
}
nav ul li a {
    color: #fff;
    text-decoration: none;
    font-weight: bold;
    padding: 10px 15px;
    display: block;
}
nav ul li ul {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    background-color: #333;
    padding: 0;
    margin: 0;
    list-style: none;
}
nav ul li:hover > ul,
nav ul li:focus-within > ul {
    display: block;
}
nav ul li ul li {
    position: relative;
}
nav ul li ul li ul {
    display: none;
    position: absolute;
    top: 0;
    left: 100%;
    background-color: #333;
}
nav ul li ul li:hover > ul,
nav ul li ul li:focus-within > ul {
    display: block;
}
nav ul li ul li a {
    padding: 10px;
}
main {
    padding: 20px;
}
section {
    margin-bottom: 40px;
}
h1 {
    border-bottom: 2px solid #333;
    padding-bottom: 10px;
}
article {
    margin-bottom: 20px;
}
article h2 {
    color: #007BFF;
}
footer {
    background-color: #333;
    color: #fff;
    text-align: center;
    padding: 10px 0;
    position: relative;
    width: 100%;
    bottom: 0;
}
#to-top {
    position: fixed;
    bottom: 20px;
    right: 20px;
    background-color: #007BFF;
    color: #fff;
    padding: 10px;
    border-radius: 50%;
    text-align: center;
    text-decoration: none;
}