Just press the flag and move your mouse around. For a crazy effect press and hold space. When you let go of space, it will go back to the original mouse trail. Enjoy! :)
I learned how to make the basics and some of the effects of this from a Scratch tutorial, my friend helped me make the clones get bigger, but the rest I figured out myself, and I made this myself. The tutorial really helped, thanks Scratch. :) The space bar thing was just me messing around with different effects to make it crazy, and then I realized I could incorporate it in because I thought it was funny, without deleting the rainbow cloud mouse trail. P.S. Probably don't press space if you can't handle quickly flashing lights...?