This is the basic figure of the Deltoid generated by a circle rolling inside another fixed circle with radius three times the radius of the rolling one. The various aspects and connexions of the deltoid with Wallace-Simson lines and orthopoles are discussed in Deltoid.html .

The 17 controls can be set in two stages each: hidding/non-hidding. They result 2^{15} = 32768 possible figures. Some of them are discussed in the file Deltoid.html . See there for references. Moving point (t) makes the circle with center Q roll into the circle passing through {A_{2},B_{2},C_{2}} and generate the deltoid.