It might derp-out the first time you press the green flag so you might have to press it agin. You can click on the drawey thingy to make it go away to see your drawing better. and you can press space to make it come back to draw some more. :)
the turning might make you dizzy and if it does you can click on it and it will disappear. (press space to make it came back--but it will still spin)
