Different ways of using perpetuum mobile. It's a nice office accessory which can relax you.
How to make this simple and very good flying airplane
Easiest way to build an origami cube and it takes less than 5 minutes.
Joined in this way, Moebius Band has a single side. If you pierce it in two it will double its size and pierced in three it will separate in two bands, one twice as long as the other
Interesting positioning of the pieces makes an extra square appear
Simple math prank for your friends. The trick is that you cannot simplify by (x-y) because it equals 0, so it's impossible.
Run command which sets a timer till shutdown
Simple and useful trick for documents security. It is same method for Excel documents