body {
    font-family: Arial, Helvetica, sans-serif;
    background-image: url('background.jpg');
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    text-align: center;
    margin: 0;
    padding: 20px;
}

h2 {
    color:#333;
    font-family:fantasy;
    font-weight: bold;
}

.tree{
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
}

.tree ul {
    list-style-type: none;
    padding: 0;
}

.tree ul li {
    margin: 10px 0;
    position: relative;
}

.tree a {
    text-decoration: none;
    color: darkblue;
    font-weight: bold;
    padding: 8px 12px;
    border-radius: 5px;
    transition: background 0.3s ease-in-out;
    display:inline-block;
}

.tree a:hover {
    background: darkblue;
    color: white;
}

/*Arrange "Volunteer,Table,User Profile,Feedback...*/
.tree > ul > li > ul > li > ul {
    display:flex;
    flex-wrap: wrap;
    gap: 10px;
    justify-content: center;
}

.tree > ul > li > ul > li > ul > li {
    display: inline-block;
}

.node {
    background-color: white;
    border: 2px solid darkblue;
    border-radius: 50%;
    padding: 10px;
    width: 120px;
    text-align: center;
    font-weight: bold;
    position: relative;
    text-decoration: none;
    color: darkblue;
    display: inline-block;
    transition: 0.3s;
}

.node:hover {
    background-color: darkblue;
    color: white;
}