To start, hit the space bar. The shape in the middle of the screen will change shape depending on how you move the mouse(or finger). You can switch to using arrow keys by hitting the a key. The d key will switch back to mouse control. This game was a random thing, trying to see how many different things that you can do with Scratch. So far, there are tons of things to do, and I do not think I can share them all, but I will just say there are a lot! This shows that Scratch can do more than just games, so do not limit your self!
