puzzle may be defined as a problem or enigma that tests the solver's cleverness and ingenuity. Games often contain multiple puzzles within them to challenge players. 

In The Art of Game Design: A Book of Lenses, game designer Jesse Schell defines a puzzle as "a game with a dominant strategy" (that is, a set of actions which always results in a solution). The most interesting part of a puzzle is trying to find this strategy -- unlike a game, a puzzle ceases to be fun after it is solved.