Gray canvas, chalk brush - blunt chalk 10, artists rough paper, & oval selection tool to make a circle.
I thought this was an interesting exercise. In the "paint inside selection mode" I painted
strokes in the circle selection and all the strokes stayed inside the selection. Then I switched
to another drawing mode "paint outside the selection" and all the strokes of color stayed outside
of the selection. A third drawing mode allows you to paint anywhere.