Top button toggles between 2- and 3-circle mode. If you'rein3-circle mode and exactly two of the circles are shaded, thosearethe ones that are brought over to 2-circle mode.
Second button toggles between worksheet and puzzle modes.
Mouse is either in size or shading mode; the current modeisindicated in the upper right. Change mode using the 2nd tobottombutton.
Bottom button determines union or intersection mode. Whenyouclick on the point of intersection of two or three circlesyoueither get the union or the intersection of the circles.
Union button forms the union (in purple) of the selected blueandpink regions.
Intersection button forms the intersection (in purple) oftheselected blue and pink regions.
Yin-Yang button forms the complement of the selected region.
Push and Pop and for the stack that rememberspurpleselections.
"Size form Sum" button calculates the size of the shadedblueregions.
"Size from Diff" button calculates the size of the purpleregioncontained inside a known blue region.