raster image of masking-intro-01-f

The rules are different regarding the geometry of a shape when clipping and masking. For example, a clip-path does not take into account the stroke of the shape used for clipping. It is however, used when masking.

The UA should render at the top of the illustration, two identical darkblue circles. Below those two cicles, two more circles should appear. They are of lighter appearance, the one on the left has a darker and thick stroke.