I heard this puzzle on the MathFactor podcast (which I highly recommend). If you don't know what Asteroids is (somehow), here's a youtube video: If you fly off the right side, you reappear on the left side, and vice versa. If you fly past through the bottom, you reappear at the top, and vice versa. So, if this were a Universe, what would the shape be? a. A sphere b. A torus c. A cylinder I made a pictorial solution which I'll post after a few people have responded.