* {
    color: #dddddd;
    background-color: #333333;
}

body {
    width: 50%;
    margin-left: auto;
    margin-right: auto;
}

div.ref {
    /* width: 50%; */
    /* margin-left: 25%; */
    /* margin-right: 25%; */
}

.center {
    text-align: center;
}

img.ref {
    width: 75%;
}

.color-box {
    width: 20px;
    height: 20px;
    display: inline-block;
    /* background-color: #ccc; */
    /* position: absolute; */
    left: 5px;
    top: 5px;
}

h1 {
    font-size: 5em;
}

h2 {
    font-size: 4.2em;
}

h3 {
    font-size: 3.4em;
}

h4 {
    font-size: 2.6em;
}

p,
li {
    font-size: 1.5rem;
}

.collapsible {
    background-color: black;
    color: white;
    cursor: pointer;
    padding: 18px;
    width: 100%;
    border: none;
    text-align: center;
    outline: none;
    font-size: 2.0em;
}

/* Add a background color to the button if it is clicked on (add the .active class with JS), and when you move the mouse over it (hover) */
.active,
.collapsible:hover {
    background-color: #777777;
}

/* Style the collapsible content. Note: hidden by default */
.content {
    padding: 0 18px;
    display: none;
    overflow: hidden;
    background-color: #333333;
    border: solid #777777 3px;
}