Spacebar to advance a frame, 0 to go back.
An updated, easier to understand, and better, tutorial on how to make Multiplayer games. If you need help, comment below. Updated basic example project: https://scratch.mit.edu/projects/92491388/ Here's an example project using just the basics: http://scratch.mit.edu/projects/19588793/ Here's an example of a (somewhat) complete game made using this method: http://scratch.mit.edu/projects/10131507/ The Original Project: http://scratch.mit.edu/projects/10148982/ Updated 11/4/14: Added an extra info tab for helping people with issues. This will answer the most commonly asked questions.