* {
    font-family: monospace;
    font-size: 17px;
}

html,
body {
    height: 100%;
    background: #111;
    color: #999;
}

body {
    margin: 0;
    display: flex;

    /* This centers our sketch horizontally. */
    justify-content: center;

    /* This centers our sketch vertically. */
    align-items: center;
}

button {
    border: none;
    background: #444;
    color: #bbb;
    padding: 5px 10px;
}

button:hover {
    background: #888;
    color: white;
    cursor: pointer;
}

/* https://www.w3schools.com/howto/howto_css_custom_checkbox.asp */
/* Customize the label (the container) */
.container {
    display: inline-block;
    position: relative;
    padding-left: 25px;
    color: #999;
    cursor: pointer;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}

/* Hide the browser's default checkbox */
.container input {
    position: absolute;
    opacity: 0;
    cursor: pointer;
    height: 0;
    width: 0;
}

/* Create a custom checkbox */
.checkmark {
    position: absolute;
    top: 0;
    left: 0;
    height: 20px;
    width: 20px;
    background-color: #222;
}

/* On mouse-over, add a grey background color */
.container:hover input~.checkmark {
    background-color: #555;
}

/* When the checkbox is checked, add a blue background */
.container input:checked~.checkmark {
    background-color: #2196F3;
}

/* Create the checkmark/indicator (hidden when not checked) */
.checkmark:after {
    content: "";
    position: absolute;
    display: none;
}

/* Show the checkmark when checked */
.container input:checked~.checkmark:after {
    display: block;
}

/* Style the checkmark/indicator */
.container .checkmark:after {
    left: 7px;
    top: 2px;
    width: 5px;
    height: 10px;
    border: solid white;
    border-width: 0 3px 3px 0;
    -webkit-transform: rotate(45deg);
    -ms-transform: rotate(45deg);
    transform: rotate(45deg);
}