You are the mouse and are trying to run away from the cat, and if you touch the cat, you lose. You use the arrow keys to move and try to touch the cheese, which will give you 1 point. If you reach 5 points, a bear will appear and try and get the cheese too. If you or the bear touches the cheese, it instantly appears somewhere else.
If you find a bug or want me to add or take away anything, just write it in the comments so I know.