It draws a triangle and fills it with pen. Drag the nodes at the vertices of the triangle to change the triangle's shape Use the arrow keys to move the triangle along.
It travels between two of the nodes, but as it does so, it makes trips to the third node to fill the triangle. This is an incredibly slow method. I think the fastest method is to fill it with the biggest circle and then of the remaining section, put the biggest circle, and then again, and again.. until the triangle is filled.
