/* element name selector */
body {
    font-family: Arial, sans-serif;
    margin: 10px;
}

/* class name selector */
.intro {
    background-color: #eee0ca;
    color: cream;
    padding: 15px;
}

/* id selector */
#tree-diagram {
    border: 3px solid #000000;
    max-width: 600px;