body {
    font-size: 16px;
}

canvas {
    border: 1px solid #999;
    border-radius: 0.5rem;
}

section {
    padding-bottom: 1rem;
}

.color-picker
{
    cursor: crosshair;
}

.pen-color
{
    /* structure */
    display: inline-block;
    height: 2em;
    position: relative;
    top: 0.5em;
    width: 2em;

    /* presentation */
    border-radius: 1em;
}
.pen-color.black
{
    background-color: black;
}
.pen-color.blue
{
    background-color: #0378A6;
}
.pen-color.green
{
    background-color: #13B813;
}
.pen-color.maroon
{
    background-color: #5C2121;
}
.pen-color.red
{
    background-color: #B9121B;
}
.pen-color.seagreen
{
    background-color: #029E9A;
}
.pen-color.yellow
{
    background-color: #FFBD07;
}

.pen-color + .pen-color
{
    margin-left: 1em;
}