Puzzle Games

Puzzle Games

Many single-player computer games contain puzzles. In action games, you often have to figure out the boss opponent 's weakness. Adventure games are full of puzzles, frequently about obtaining inaccessible objects or getting information from other people. Even first-person shooters have the occasional puzzle, figuring out how to get past locked doors and other obstacles. Puzzle design is an essential element of game design, and it's harder than it sounds.

Puzzle games are games that are primarily about puzzle solving, sometimes without incorporating the puzzles into a story line or larger goal. That doesn't mean that they're a random collection, however. Puzzle games are usually variations on a single theme. To be a commercial success, a puzzle game needs to be challenging (but not too hard), visually attractive, and, above all, enjoyable to play with. It also needs to be fresh and large enough to justify spending the money on. Although solitaire card games such as FreeCell belong in the class of puzzle games, unless you sell a lot of them together as a collection, people are unlikely to want to pay for them.

Scott Kim's Eight Steps

Scott Kim is a designer who creates puzzles for the print media, web sites, and computer games. He has worked in the field for many years and has identified eight steps in puzzle game design. The first four steps comprise the process of specifying the rules, while the last four comprise the process of building the puzzles and the game itself:

1. Find inspiration. This can come from a variety of sources, including other games. Tetris , for example, was inspired by a noncomputer game called Pentominoes. You can be inspired by a piece of art (the drawings of M.C. Escher have a very puzzlelike feel), a story, or some particular subject matter. Another source of inspiration is a play dynamic of some kind: flipping switches, turning knobs , sliding objects around, or picking them up and putting them down. Or, there are more complex dynamics among objects: balancing, reflection, connection, and transmission.

2. Simplify. Suppose you have an idea for a puzzle: efficiently parking vehicles of different sizes in a crowded parking lot so that when someone asks you to retrieve their car, you have to move as few other cars as possible. Part of making this task fun is simplifying it to its essentials. First, identify the essential tricky core skill (in this case, space planning on the fly) and concentrate on that. Second, eliminate any irrelevant details. Don't make your player worry about crashing the cars, for example. Third, make the pieces uniform. Instead of having cars with infinitely variable shapes and sizes, it's better to have several standard types that conform to a square grid. Finally, simplify the controls. Figure out what the essential moves are, and devise controls that implement them with a minimum of fiddling.

3. Create a construction set. The only way to be sure that a puzzle concept works is to play it, but obviously you don't want to code up the whole game before you know whether it's fun. You can build a paper prototype or a simple version in something like Macromedia Flash to see if it works. The rule designer can play with it to tweak the rules, and later the level designer can use it to build levels. You can also code a construction set into the final game so that players can construct puzzles for each other.

4. Define the rules. This is the key part of puzzle design. Most puzzles are characterized in terms of four things: the board (Is it a grid? A network? Is it irregular? Or is there no board at all?), the pieces (How are they shaped? What pictures are on them? What other attributes do they have? Where do they come from?), the moves (What is allowed and what is not? Are they sequential or simultaneous? What side effects do they have?), and the goal or victory condition (Does it have to be an exact match, or will a partial one do?).

5. Construct the puzzles. A puzzle challenges the player to get from a problem to a solution, but, of course, the path isn't simple. Every puzzle requires that the player make choices, some of which lead to dead ends. In an adventure game, each puzzle appears in a larger context (the story) that gives it meaning, and solving it advances the plot somehow. Some puzzle games also offer an overall plot of sorts or won't let you try the next puzzle until you've completed the current one. Good puzzles require insight from the player, that "Aha!" moment that occurs when the player realizes how the puzzle works and how to solve it. But you mustn't require an insight that's too obscure, or it will feel unfair. If you tell the player that he's in a maze, it's unfair for the only solution to be to knock down the walls unless you indicate somehow that this is possible.

6. Test. Testing tells you several things. It tells you whether the puzzle is too easy or too hard (this can be difficult to predict in advance), and it also tells you whether it's fun in the first place. It helps you find out if there are alternate solutions that you didn't think of, and it helps you discover errors in the rules. And, of course, it lets people try out the user interface. Because puzzle actions tend to be repetitive, it's important that the interface be smooth and not frustrating.

7. Devise a sequence. Now it's time to order all your puzzles into a sequence. The most obvious arrangement is a linear or accelerating sequence going from easy to difficult, but in practice, that becomes tiring and discouraging. A better arrangement is a sawtooth shape, which gets difficult for a while, then goes back to an easy puzzle, and so on, over and over. And, of course, you can give the player the freedom to play the puzzles out of order or let her earn it. You also need to think about transitions between puzzles, something that will keep her moving on to the next one. War games and role-playing games often do this with a story line. Or, the player can be working on a metapuzzle in between the regular puzzles, which motivates her to complete the whole game.

8. Pay attention to presentation. Finally, of course, there are all the other details of game design: sound, graphical style, animation, user interface elements, story line (if any), and so on. If you're used to designing other kinds of games, it might be tempting to move this to an earlier point in the process, but with puzzle games, the puzzles are 90% of the battle. Get them right first, and the rest won't be nearly as hard.

What Computers Bring to Puzzles

Computers enable us to make a lot of puzzles that would be impossible or very expensive to create in the real worldall the mechanical parts in The Incredible Machine , for example. But even if a puzzle is physically possible, the computer can add a number of useful features to make the gameplay easier and more enjoyable.

• Enable nonphysical or awkward moves. The computer can let players do things that don't correspond to physical actions in the real worldfor example, changing the color of something. You can also let the player control several things at once with just one key, something that would be awkward to do in a physical implementation.

• Include computation features. You can use the computing power available to automatically generate new puzzles, find solutions to the current puzzle, or generate hints about what the player should do next.

• Enforce the rules. In a lot of physical puzzles, it's up to the player to enforce the rules on himself. Sometimes players make mistakes and break the rules accidentally . A computer game can make sure that never happens.

• Undo and record moves. This very useful feature for games involves moving objects around in a sequence, as in Solitaire.

• Structure the experience. The computer allows you to present the experience in a particular order, if necessary, passing automatically from one phase to another, if that's what your game requires. In the real world, the player would be looking at the instructions and saying, "Let's see, what am I supposed to do next?"

• Teach. You can include tutorial modes and step-by-step instructions to help your player get into the game.

• Utilize bells and whistles. Obviously, with sound and animation, you can make a puzzle much more aesthetically interesting on the computer than it would be as a physical object.

• Enable online play. The computer lets players compete against one another, compare solutions, and be part of a puzzle-solving community.

Checking the Victory Condition

Bear in mind that players don't always find the solution to a puzzle the same way that you did when you invented it. There might be more than one path to the goal. When your game is checking to see whether the puzzle has been solved , you should test only to see if the player has met the victory condition you gave her, not that she has done it in the way you expected. Otherwise, you've cheated her, and she'll be very frustrated. She's managed to get to the correct solution state, but your game refuses to recognize it.

This problem occurred in the game Interstate '76. It wasn't a puzzle game, but one of the levels did contain a puzzle of sorts. The player was driving an armed and armored car around in an area enclosed by a concrete wall, and the victory condition for winning the level stated that (among other things) it was necessary to get out of the enclosed area somehow. The game's designers had put in a hidden ramp, which they wanted players to find and use to drive out of the area. However, players of the game discovered that there was another way to get out. If a player dropped a land mine near the wall and then drove toward it at full speed, the force of the explosion would lift the car high enough to clear the wall, and the car would fly over it and out. Unfortunately, the software didn't test for the solution state given: Is the car outside the wall? Instead, it tested to see if the ramp was being used. If a player got out without using the ramp, it didn't know that the level was finished, even though the victory condition had been met.

Of course, sometimes games contain bugs that allow a player to cheat in some way and reach a solution by a means that's completely outside the rules. In Interstate '76 , however, the trick with the land mine wasn't a bug; it was just an innovative solution that the designers didn't consider. When the software is checking the victory condition, be sure it's checking the solution state that you told the player to achieve, not the way in which he achieved it.

Case Study: The Incredible Machine

The Incredible Machine is an excellent example of a puzzle game that is imaginative and clever and that has sold really well. In fact, it's not just a game, but a whole game franchise, with five editions so far. The current version is called Return of the Incredible Machine: Contraptions , and it's published by Sierra Entertainment (formerly Sierra On-Line).

The game consists of a series of puzzles, each of which involves building a Rube Goldberglike machine to accomplish a certain task. Each machine is constructed in a two-dimensional space upon which a variety of mechanical devices can be placed. (Some of these devices are actually animals, which can be frightened by noises or lured by food.) A few objects are already in position at the beginning of the puzzle, and the victory condition states what the player is trying to accomplish (for example, pop the balloon). The player is given a limited number of additional devices to place in the area. The object is to place them and hook them up in such a way that when the machine is set in motion, the goal is achieved. Playing the game consists of adding elements to the machine, trying them out, adjusting them, trying again, and so on. Figure 16.2 shows one of the scenarios in The Incredible Machine. The goal is given at the left. Available parts are in the area beneath the main workspace.

Figure 16.2. The Incredible Machine.

Scott Kim has identified three key design decisions that he feels have made The Incredible Machine the prototypical construction puzzle game.

1. Allow the player to build things. This makes The Incredible Machine a construction game and differentiates it from, say, Tetris (an action puzzle game) or Marble Drop (a logic game in which you decide where and when to drop marbles into a mechanism). The player feels as if he is exercising his creativity.

2. Include no real-time decision making. Constructing the machine and running it take place in separate modes. The player can take as long as he wants to think about what he's doing. This is in contrast with Lemmings , which is also an excellent game but requires the player to solve the puzzle on the fly. Often if the player didn't get it figured out in time, he had to start over.

3. Allow players to design their own puzzles. Any time players can build their own elements, it adds value to the game and helps create a community of devoted fans. Players can exchange their puzzles by email, post them on web sites, run tournaments, and enjoy all kinds of other activities, all of which is free publicity for the game.