This little device will fool your friends and make them you think that you have supernatural powers (not guaranteed)!
This is the basic idea: there are two axles sticking out of a huge block of LEGO. When you turn one of the axles clockwise, the other axle turns clockwise. But when you turn the axle counter-clockwise, the other axle still turns clockwise. How? Well, just look through this instructable. The box is made only out of LEGO, you need nothing else. The box is fairly small, and the action is very fluid, it is not at all jerky. This instructable will show how to build the box.
Step 1: Making the Axles
There are three axles and five gears within the box. This step will show you how to make them.
Step 2: Assembly
Now you have to assemble the box.
Step 3: Instructions for Use
If you rotate the top axle clockwise, the bottom axle will also rotate clockwise. But if you rotate the top axle counter-clockwise, the bottom axle will still rotate clockwise! See if your friends can figure out the mechanism!