iwmlib/css/highlight.css

circle {
    stroke: white;
    fill: transparent;
    stroke-width: 8px;
}

mask circle {
    stroke-width: 0;
    fill: white;
}

.addedImage {
    filter: invert(1);
}

.debugRect {
    stroke: red;
    fill: transparent;
    stroke-width: 8px;
}