Ooooh, this is really cool!
Honestly, I think something that'd really help is having skew and rotation snap to discrete steps the way the grid does - that way, it'd be easier to play with things and reverse engineer how a shape was created. Maybe also a popup for the target shape's transformation matrix as well as your current transformation matrix? That being said, I adore the sound design, presentation, etc. - this is REALLY good.
Well done!