Press space to alternate between a sprite with a costume; and the same sprite without a blank costume, and see how differently they behave
This is a bug, but I'm not sure whether its just me experiencing this, or if everyone will. what i see is the non costumed sprite behaving predictably but randomly, and the costumed sprite acting as expected. (check inside to see i didn't add anything other than a mouse tracking script, some pen, and a costume change scirpt)
