Working Definition: A puzzle is a mental challenge presented to the players of an RPG, with consequences for their characters.
This definition gives us two elements we need to create for every puzzle scene. First, what is the mental challenge? Second, what are the consequences? It also creates hard boundaries. These are the corollary rules that emerge from the definition of an RPG puzzle:
- The challenge is overcome by actions the players take, not the characters. Game system should have little or no chance of overcoming the challenge.
- Solving the puzzle cannot be the only way to move the story forward.
Here's an illustrative example:
If you're running Trail of Cthulhu, and your investigators find an encoded message written to a 16th century Ottoman king, they can decipher it using the Cryptography skill. If you intend to use the game system to resolve the clue, there is no puzzle. However, let's say you want to add a puzzle. You might encipher the clue using a simple substitution cipher, and allow any characters with Cryptography to attempt to decipher it. If they use a Cryptography spend (see the GUMSHOE system), you can give them the key, so they can simply decode it. In this case, the players have a choice whether to bypass the puzzle with the game system.
This is not a very good puzzle scene because 1) the challenge can be overcome with character abilities, using the game system, and 2) the consequence of failing to decipher the puzzle is that the characters don't get the core clue needed to advance the story. Let's rework the puzzle to fit into our rules about puzzle scenes...
Your investigators find an encoded message written to a 16th century Ottoman king. They can decipher it and get he core clue using the Cryptography skill. If they have Cryptography (and they will, because of how the game works), they automatically get the clue needed to move the game forward. Then they notice that the last paragraph does not decipher correctly. It's in some ancient tongue... The GM hands them another enciphered page. There is no core clue here. They have to decipher the code themselves (as players) to get the information it contains. This represents the characters puzzling out a language not of this earth. If they solve the code, the plaintext is a disturbing invocation to an alien being. Later, when the PCs encounter an alien that matches its description, they can say the invocation and it will hesitate, allowing them to take a round of actions to run away - or foolishly shoot at it.
Now our example cipher is a challenge that the players have to solve, with consequences on the characters, that does not violate our corollary rules.
When building a puzzle, you combine two elements:
- The challenge the players have to solve; and
- The consequences for their characters
Challenge elements include...
- Ciphers. The challenge of ciphers is that it's hard to make a cipher both challenging to solve and possible to solve. Players can usually decipher substitution ciphers eventually, and most codes that can be solved by hand are variants on substitution ciphers. When done well, the challenge of a cipher is realizing there's a cipher in the first place. Say there are images of different devils on the walls of an ancient fane, and the first letters of the names of the devils pictured spell out the keyphrase that the PCs can say to an animated iron door to make it open. The players might realize that there's a cipher if they realize there are a lot of similar images of Erinyes...
- Riddles. In the age of the internet, it takes about an hour to find a handful of amazing, brilliant riddles of varying difficulty levels. Riddles are fun, but the players may be tempted to cheat using the game system, such as casting Charm Person spells, intimidating the riddle-giver, and just taking what they want. One way to prevent this is to make the consequence of success have to do with the riddle giver itself (an animated portcullis is a personal favorite - break it or disenchant it and it's stuck!). Alternately, you can think through the different things your players might try to use to cheat if they get frustrated. Remember, puzzles never prevent the story from going forward, so failure is possible!
- Math and logic. There are hundreds of classic math and logic puzzles you can look up, from number sequences to logic riddles, to chess puzzles, and more. Math teachers love these things, so try browsing educator websites for free resources. You just have to re-skin the puzzle to your setting. Choose puzzles appropriate to your game's themes. In Trail of Cthulhu, an astronomy logic puzzle might be great. In D&D, a number sequence could be woven into a sphinx's shroud, encoded in geometric shapes.
- Darmok and Jalad puzzles involve a clue delivered in such a way that the players have to learn the lore of a culture or facts that the clue-writer knew to decipher it. They work great for ancient ruins, where a clue like "the supplicant brings King Jorod's Blessing before the Holiest Tree and anoints it as Kalyx'zshar to her wyrmlings." They have to learn that King Jorod bestowed the Ancient Prophet with a gift of wine, the Holiest Tree is a fir, and Kalyx was a red dragon who warmed her wyrmlings in a roaring fire. So the puzzle is solved when the PCs pour wine in the chalice printed with a fir tree, then heat it with flame.
- Minigames. Games like mastermind, minesweeper, battleship, chess, and connect four can be re-purposed into puzzles for your game. Choose a game that evokes the feel of the puzzle that the characters are working to solve. For instance, a steampunk setting computer could be hacked with a Mastermind-style guessing game. A dragon might be willing to give up some treasure if the PCs can beat her at 20 questions. A vampire might challenge the PCs to a chess match for the fate of a kidnapped paladin.
- Pattern recognition. Sometimes the best puzzles are the simplest. Throughout the dungeon, icons of revered, trusted, helpful things are painted blue; and reviled, hated, dangerous things are painted green. At the end of the dungeon -- or better, at the beginning -- are two chests. One has a blue-painted top and the other a green-painted top. Though they're not locked, if the players open the green one, both chests will be consumed in fire, destroying their contents and burning the fool who didn't pay attention.
- Mazes. A common puzzle in D&D is a maze -- an area that the players get lost in. The GM describes the corridors, expecting the players to map the area to keep track. The GM is cunning and uses multiple levels to stymie the "right hand rule." Almost always the consequence for navigating a dungeon maze poorly is traps and monsters. Traps that reset and monsters that "restock" are even better -- punishing players for doubling back or wandering aimlessly. Mazes are basically a kind of Sim scene (see below).
- Social scenes can be used as puzzles (the players have to decide who's lying, who's right, choose sides, etc.).
- Sim scenes can be used as puzzles (the players have to think of a strategy to overcome an obstacle; mazes are a common Sim puzzle obstacle).
Consequence elements include...
- Rewards such as money, magic, treasure, blessings, wishes, allies, etc.
- Tactical information, such as secret passages, directions, ways to ambush enemies, ways around dangerous encounters, tactics to use against monsters, etc. In 13th Age, you might want to use puzzles as opportunities to influence the outcome of Icon rolls.
- Plot information, other than clues required to move the story forward. Examples include backstory on NPCs, deeper understanding of villains' motives, etc. Ideally, the information could impart some sort of tactical advantage (see above).
- Removal of negative reinforcement, such as a poison gas, or water or sand filling the room.
- Time. A great way to add an element of excitement to a puzzle-filled area is to create a time limit. The players now have four outcomes with puzzles: Fail to solve them and give up, failt to solve them (but take a long time), solve them quickly, or solve them (but take a long time). But now you have a built in reward/punishment mechanism. Maybe solving a puzzle adds time to the clock, or failing to recognize a pattern correctly causes a time penalty. What the timer is, in the game, is up to you. Is the volcano getting ready to erupt (D&D)? Is a nuclear missile going to launch in 120 minutes (Gamma World)? Is the infernalists' ritual coming to completion (Vampire)?
- Punishment, such as damage, curses, poison, combat encounters (which cause all of the former things), destruction of treasure elsewhere, or plot consequences (e.g. hostages killed, in a modern serial killer/terrorist scenario).
Remember that you can pair rewards for success with consequences for failure if you want. And only one of the two needs to be impressive for the puzzle to be exciting.
There are players who hate puzzles in RPGs. I know at least two such players. They really enjoy the escapist fantasy of an RPG, and don't like to cross the wall to where their own ability is tested. Perhaps they don't really enjoy puzzles in real life. Like any practiced skill, players who solve puzzles infrequently will probably be bad at it, and it may make them feel insecure; or else make them feel bad about their character, since their character will not be as strong a contributor.
Before designing a puzzle-heavy adventure, ask your players how much they like puzzle scenes. If they're at least neutral about puzzles, you're OK. If one of your players dislikes puzzles, you might be able to include one every now and then for the players who do like puzzles, but you shouldn't make a whole dungeon or adventure full of them.