Press that green flag and watch. use keys 1, 2, 3, 4, 5, and 0 to change the speed. Why not drop a comment?
Credit to dillyd for idea and scripts, I have only tweaked them. I now don't support this project, but https://scratch.mit.edu/projects/106552342/ instead. Yeah! 30 loves! 23 faves! 361 views! 36 awesome comments!