Simple but surprisingly fun puzzler. I'm suprprised by the amount of levels you were able to create. But you should look over the order of them so there is a progression in skill level.
Also, I think a nice contribution would be to have a counter for each level and a goal - "Try to finish the level in 5 placements" or similiar. Also switching between the different sizes/shapes with either numbers, 1,2,3 or scroll wheel would be a nice touch.
Was quite fun to play, didn't finish though, was too many levels that started to feel the same at the end