Press the green flag button. Scratch should run around the screen and make a high pitch if he touches a blue item, or a low pitch when he strikes a red object.
I'm not very happy with this program. It doesn't seem sensitive enough. Occasionally, Scratch will pass directly under a dot, and it won't make a single sound. It seems to have to pass through a particular point (or points) before it registers that the two sprites are touching.
