Drag with the right mouse button anywhere in the torus below (on a Macintosh, drag with the command key held down). The whole torus will "scroll". Objects that disappear off the top reappear at the bottom, and objects that disappear off the right side reappear at the left. A torus has no edges or boundaries of any sort.
All the games in this collection let you scroll with the right mouse button. Most of them let you scroll with the left mouse button as well, just so you drag the background, not the actual game pieces. Try it in the torus below.
You may return to the index to play the games, or continue with this introduction to learn about the Klein bottle.