A puzzle is a game, problem, or toy that tests a person's ingenuity or knowledge. In a puzzle, the solver is expected to put pieces together in a logical way, in order to arrive at the correct solution of the puzzle. There are different genres of puzzles, such as crossword puzzles, word-search puzzles, number puzzles, or logic puzzles. Puzzles are often created to be a form of entertainment but they can also arise from serious mathematical or logistical problems. In such cases, their solution may be a significant contribution to mathematical research.