A puzzle is a form of entertainment which presents some sort of problem or mystery which makes you think in order to figure it out. There are many common types of puzzles, including crosswords, jigsaw puzzles, riddles, puzzle games, logic puzzles, tavern puzzles and other kinds of mechanical puzzles. Also, most of recreational mathematics can be thought of as puzzles. A lot of recreational mathematics and logic puzzles fall into the category of old chestnuts.