Press the space bar to advance through the tutorial. I advise you to go through the tutorial slowly to make sure you understand it. Otherwise it might go right over your head.
My second tutorial. I know this isn't the most efficient way to do velocity, but hopefully it's understandable. Inside the project is The Script. (Duh duh duh!) Good luck! Check out my collision tutorial, Easy Collision! http://scratch.mit.edu/projects/12268614/
