Does it have a right answer? So does my letter puzzle have a right answer? It does in the sense that when shown the answer, most people will agree that this is the best answer. But what constitutes a letter is a subjective matter. For instance, in a squarish typeface, the following shapes could be interpreted as a lowercase R or a capital J: Figure 2. These shapes could be the letters R and J. I could plug this leak in my puzzle by showing the particular alphabet of letters I have in mind: Figure 3. The answer comes from this typeface.. Notice that my definition doesnt insist that there be only one right answer. If you interpret the diagram differently, there are many other possible answers. For instance, the following shapes, which could be interpreted as the letters J and G, can all be unfolded from figure 1, if we interpret the edges a bit differently: Figure 4. Other ways to unfold figure 1. "Has a right answer" distinguishes puzzles from games and other play activities. Another game designer Kevin Maroney includes puzzles as a subspecies of games. I prefer a finer-grained definition that I first heard from Chris Crawford, veteran game designer and founder of the Game Developers Conference.

In his 1984 book The Art of Computer Game Design, (still the most articulate book on the subject, and now available online) Chris distinguishes four types of play activities, ranging from most interactive to least: Games are rule-based systems in which the goal is for one player to win. They involve "opposing players who acknowledge and respond to one anothers actions. The difference between games and puzzles has little to do with mechanics; we can easily turn many puzzles and athletic challenges into games and vice versa."

are rule-based systems in which the goal is for one player to win. They involve "opposing players who acknowledge and respond to one anothers actions. The difference between games and puzzles has little to do with mechanics; we can easily turn many puzzles and athletic challenges into games and vice versa." Puzzles are rule-based systems, like games, but the goal is to find a solution, not to beat an opponent. Unlike games, puzzles have little replay value.

are rule-based systems, like games, but the goal is to find a solution, not to beat an opponent. Unlike games, puzzles have little replay value. Toys are manipulable, like puzzles, but there is no fixed goal.

are manipulable, like puzzles, but there is no fixed goal. Stories involve fantasy play, like toys, but cannot be changed or manipulated by the player. Figure 5. Four types of play, each built on the previous For instance, in the realm of computer entertainment software, Quake is a game, which includes some puzzles.

is a game, which includes some puzzles. The Incredible Machine is a series of puzzles, which includes a toy-like construction set for building puzzles.

is a series of puzzles, which includes a toy-like construction set for building puzzles. SimCity is a toy, which players make more puzzle-like by setting their own goals.

is a toy, which players make more puzzle-like by setting their own goals. Myst is a story, which happens to be told partly through puzzles. This hierarchy leads me to a useful rule of thumb for puzzle designers: to design a good puzzle, first build a good toy. The player should have fun just manipulating the puzzle, even before reaching a solution. For instance, players can enjoy rotating and manipulating blocks in the action puzzle game Tetris even if they dont understand the goal.

Puzzles are solitary affairs, unlike games. Herb Levy, in his GamesCafe column "Nature of the Beast," sings the praises games as social activities. One of the main challenges for me as a game designer is to find ways to introduce some of the thrill of competition back into puzzle games.

As Maroney points out, the card game Solitaire is an interesting borderline case between game and puzzle. We normally call Solitaire a single-player game, but in fact it is a kind of puzzle, since any given deck has a definite solution (or sometimes no solution). Shuffling the cards is a way to randomly generate a new puzzle.

Other types of puzzles that walk the line on the issue of right answers include trivia questions (which require knowledge of the world), dexterity puzzles (which could be classified with sports), puzzles involving chance (in which the player does not completely control their own fate), and poll-based questions (in which the rightness of answer depends on what everyone else answers).