Well, I have created what may possibly be the first virtual trackball on Scratch. Drag mouse inside white circle. You can spin it by moving the mouse faster.
There may be some glitches. I used only directional comparisons and did not rely upon x and y values. I did use sin in its simplest way. Something is missing, but I am not sure what. I know it is not perfect, but I have not yet seen a trackball on Scratch, so I made 1.
