Multiplayer Puzzles
By Scott Kim

This article originally appeared in The Games Cafe, a now defunct web site devoted to lovers of board games and puzzles.

Every year I host a roundtable discussion on the subject of puzzles in computer games at the annual Game Developers Conference in San Jose, California. I start by asking people what issues they want to discuss.

One of the most frequently raised issues is multi-player puzzles: can you create a puzzle for several people to play together? Although I'm intrigued by the possibility of multi-player puzzles, I'm surprised that so many other people are interested too. After all, in the world of physical games there is a clear division between multi-player games, like Monopoly, and single-player puzzles, like Rubik's Cube. No one seems to be clamoring for single-player Monopoly or multi-player Rubik's Cube.

Most puzzles don't make good multi-player games The issue of multi-player puzzles come up naturally for computer games because computers make it possible to create single-player games that are much more active and engaging than physical solitaire games. So most computer games are single-player. On the other hand people still like to play with other people. As a result, computer game players have come to expect games to have both single and multi-player modes.

Here are eight ways to create multi-player puzzles, based on ideas from the Game Developers Conference discussions.

Some puzzles are already multi-player

Let's start with the obvious. Any puzzle designed for one player can also be played by more than one player. Players can collaborate, take turns, or offer hints to each other. Jigsaw puzzles work particularly well for groups because pieces are spread over a large area, and portions of the puzzle can be solved separate from the rest of the puzzle. In contrast, mazes do not work well for groups, since there is a single point of attention.

Of course there's nothing inherently multi-player about a jigsaw puzzle. At any time one person can take over and solve the puzzle. What about puzzle games built for multiple players?

Competitive puzzle games

The simplest way to turn a puzzle into a multi-player game is to make it competitive. For instance, the popular game Tangoes includes two sets of tangram pieces, so that two players can race to see who can complete a given figure first. Board games and game shows like Trivial Pursuit and Jeopardy! are are essentially a series of separate puzzles, connected by cumulative score. (Trivia questions are at the edge of what I consider a puzzle, but you get the point.)

There are also games based on puzzles. Scrabble is based on crossword puzzles. The movie 2001: A Space Odyssey as originally shot included a scene in which astronaut Dave Bowman plays a game based on the pentomino puzzle pieces. Cathedral is a board game based on polyominoes in which the last player to be able to place a piece on the board wins. Hexcite is a recent computer game based on polyamonds (pieces built of triangles). In all of these games player take turns making moves on a single playing field.

The computer game Tetris created a whole genre of what I call action puzzle games, in which a player tries to solve a puzzle that is in constant motion. In multi-player versions of Tetris players play simultaneously on separate play fields. Speed matters; hesitate and the situation keeps getting worse. Other popular action puzzle games include Puzzle Fighter and the recent Chu-chu Rocket for DreamCast.

All these games are fundamentally games, not puzzles. The large-scale goal is to beat an opponent, not to solve a puzzle. What about group games in which the goal is to solve a puzzle?

Mystery weekends

Mystery weekends are a good example a group game in which the primary goal is to solve a puzzle. A group of people gather in an evocative location - often a hotel - to participate in acting out a murder mystery. Each person receives a instructions for playing a character, and some of the clues. By exchanging information, players race to see who can solve the mystery first. Here the nature of the puzzle is a bit fuzzy; although there is a definite right answer, the criteria for proving that the answer is correct can be subjective.

What about group puzzles based on traditional sorts of puzzles?

One person invents, the other solves

Another way to include multiple players in a puzzle is for one player to invent a puzzle, and another to solve it. Common examples include Hangman, Battleship and Mastermind.

The puzzles in this type of game must be easy to invent. For instance, a player making up a Hangman puzzle only has to think of a word. There is still strategy though; the player may choose a word with uncommon letters, or an unusual arrangement of common letters, depending on what the player thinks might fool the other player.

Note that the two players play different roles. Players can reverse roles from game to game to even things out.

Both players invent, both solve

I like games in which players invent puzzles, but I've been bothered by having players play different roles. Recently I've started thinking about games in which both players simultaneously invent starting positions, then race to try to reach the other position.

For instance, both players could start with identical sliding block puzzles, each scramble their puzzle, then race to turn their arrangement into the other arrangement. This particular example isn't very interesting, but I feel there's potential here.

In this type of game both players play the same roles. Because players start by scrambling the same board, all puzzles are guaranteed to have solutions. By having players start in different positions, we avoid the problem that one player can observe and copy the other player's moves.

Interwoven Puzzles

Parent and Child Puzzles, by Helene Hovanec (Random House, Times Books 1996 ISBN 0-8129-2703-6) is a collection of tandem word puzzles designed to be solved simultaneously by a parent and a child. The book is opened flat and placed on a table with the parent sitting on one side and the child on the other. One page contains a parent's puzzle and the other contains a child's puzzle. Answers from one puzzle become clues for the other puzzle, so play is cooperative. The two puzzles have similar themes, but appropriately different vocabulary levels. Although the pairs of puzzles are interwoven, the cooperation is loose.

What about cooperative puzzles with tighter interaction?

Avatar-based multi-player puzzles

Many multi-player online games contain puzzles that cannot be solved by a single person. In the now defunct kid's game Castle Infinity, each player has an animated avatar (creature) that can walk around a large landscape. In order to encourage players to interact with one another, the designers of Castle Infinity included puzzles that require the presence of several avatars in order to simultaneously activate devices in different locations. One player cannot solve the puzzle alone because an avatar can only be in one place at a time. Much of the challenge of such a puzzle is social: persuading people to cooperate and coordinating their actions.

Cooperative puzzles

Now we come to one of my favorite multi-player puzzles. The Cooperation Squares is a game for five people that is often used as a team-building exercise for groups of people learning to work together.

Here's how it works. Each player gets a few flat pieces cut in the shape of triangles, squares and other simple polygons. The goal is for each player to end up with a perfect square in front of them, made by assembling pieces any holes or overlaps. All pieces must be used. Initially no player can make a square with their pieces. Players must exchange pieces in order to get a set of pieces they can make into a square.

Now here's the catch: players may only give pieces to other players; they may not take pieces or in any way tell another player that they want a piece. It is quite easy for the group to reach in a position where one player has made a square, but the rest of the players cannot all make squares. For the sake of the group, the player with the square must break up their square and distribute the pieces. Typically the groups that do best at this game are unattached to their individual squares, focusing instead on the group situation.

I liked the cooperation squares so much that I made up two harder versions: one in which all but one of the players starts with a set of pieces that makes a square (shown below), and another version in which it is possible to make squares of two subtly different sizes, only one of which is correct. I think this would make an interesting online computer game, though it would probably lose some of its social charm.

Here is my variation on the cooperation squares. Players exchange pieces until every player can make a square. The final squares are all multicolored. Can you solve it? The solution is unique. If you know of other multi-player puzzles, or have thoughts on other ways to make multi-player puzzles, I'd be very interested to hear them. Feel free to email me at