I'd like to define precisely what I do, and what I do not mean by 'puzzle' before proceeding further. Note that these are not common definitions, simply terms which I find useful to facilitate clarity of discussion.
An obstacle is anything which hinders a character's progress towards a goal. A lock would be a very basic example of an obstacle.
An obstruction is a simple, or even natural, type of obstacle. Obstructions are general-purpose, and likely identical to any number of similar obstructions of the same type. Examples of obstructions would be locked doors, walls, pits, or even most traps.
A puzzle is a more elaborate form of obstacle than an obstruction. It is almost always created by an intelligent force, and is likely unique in its design. Examples of puzzles would be riddles, a door which only opens when four statues in a room are turned to face each other, or a box with no visible lid which opens only when submerged in holy water.Puzzles are some of the most difficult obstacles to manage successfully, and should be used sparingly. In fact, a great many GMs I've spoken with over the years believe that puzzles should be considered verboten. And they have an excellent point! Puzzles can stop a game in its tracks. Almost by definition, puzzles have only a single answer. So instead of the players attempting to concoct their own solution (a great strength of tabletop RPGs) they're attempting to figure out what the GM's solution is. And if they get stuck when trying to figure that out, then the progress of the game can come to a screeching halt. And that's when people start looking for a new GM.
But I hold that puzzles have their place. Maybe it's it's simply because the early Legend of Zelda games are near and dear to my heart. No dungeon, temple, or crypt seems quite complete without a puzzle. Recently I ran a game where the players faced several puzzles crafted for them as a test by a master illusionist. All of the puzzles challenged my players, without becoming game-stoppers. I'll use those puzzles as examples.
Puzzle The First
GM says: "You enter what appears to be a small grassy field within the tower. The walls and ceiling are made of dirt, and a dirt path at the far end of the room leads down. There are [number equal to the number of characters present] horses present, docilely grazing."
Additional Information: The horses were very friendly, and could be ridden easily. If any character attempted to walk down the dirt path, they were asked to make a reflex save. Failure meant they fell into the path as though it were water. A round later they fell out of the walls or ceiling of the room, taking one point of damage. After one player did this, the voice of the wizard filled the room with "Your feet won't work there! You'll need these!" and as he speaks, clovers sprout from the grassy ground.
Intended Solution: The players were supposed to ride the horses down the dirt path. If they did, they would suffer no adverse affects. The clovers were a hint about cloven feet, but if they'd strapped the clovers to their feet somehow, I would have allowed them a half-success. They would sink up to their waist, and be able to slog their way down the ramp. I also would have accepted simply jumping off the edge, down to the bottom of the ramp. Though though as it was a 20ft drop, falling damage would apply if they didn't make a successful acrobatics check.
What they did: My players were, at first, very wary of the horses. Just outside the tower they had been dealing with a stampede of horses, and didn't want to get thrown off another raging horse. They did attempt to walk down the ramp, and triggered the hint. Someone suggested strapping the clovers to their feet, but before anyone tried that, one of my players decided to mount a horse and go for it. It worked, so everyone followed suit. The entire puzzle took perhaps 3-5 minutes to solve.
Puzzle The Second
GM Says: "This is a small room with a stone floor. There is a line on the floor ten feet away from a door opposite where you entered. The line is painted on a single, long piece of stone, and beneath it is written in common 'You must stand behind this line to open the door.'"
Additional Information: The stone which the line is printed on is 12ft long, and loose. Characters can pry it up easily, and beneath it is a 15ft coil of rope. The door is on on hinges which allow it to open both in or out. Pushing on the door while between the line and the door will be next to impossible. However, the door will open easily to even small amounts of force, so long as the originator of that force is behind the line.
Intended Solution: None, really. Though I did have three expectations of how the puzzle might be solved: The 12ft long piece of stone might be used to push the door open, the rope might be tied to the door, and pulled from behind the line. Or, alternatively, the players might throw heavy objects (or even each other) at the door.
What they did: My players really surprised me with this one. Rather than doing what I expected them to do, they first tried to open the door by taking the rope they found beneath the stone, and laying it out right next to the door, then trying to push the door open. When this didn't work, they tried the same thing, but this time they moved the stone with the line on it. Given the way I worded the rules, I decided that this should work, and allowed them to open the door. However, if I had decided that the line was somehow intangibly tied to its original spot, I think my players still would have figured the puzzle out promptly. This one was quick. Perhaps 2 minutes tops.
Puzzle The Third
GM Says: "There are 5 buckets hanging on the wall with labels on them. Each apparently has a different color of paint in it--red, blue, green, yellow, and black. Across the small room from the entrance is a plain door.
Additional Information: Behind the door is a stone wall. However, when the door is painted, opening it creates a portal based on the color used. The color/portal associations are as follows: Red opens a portal to the doorway the PC's entered this room through, Blue successfully allows the PCs to progress to the next room, Green opens a portal to the first layer of hell, yellow causes those who pass through the portal to simply come back out of the portal again, and black opens into space looking down on the planet (a wall of force stops any air, or players, from going through the black door.) The labels describe these locations, but are written in gnomish (the language of the illusionist who created this trial). This was intended as a hint to the illusionist's identity. He had thus far presented himself as a 9-ft tall humanoid.
Intended Solution: To paint the door blue.
What they did: My players probably struggled with this one the most. I probably should have provided better clues. Rather than paint the door, they painted the stone wall behind the door, but I decided to allow it. It took them perhaps 5 or 6 minutes to progress past here.
Puzzle The Fourth
GM says: "There are three iron doors exiting this room. High on the wall is a window made of grass. A green light filters into the room, the blades of grass creating a collage of lines and edges over every surface the light touches. In the center of the room is a large lens mounted on two axes so it can be turned in any direction. It is presently focusing a small beam of light onto the floor, warping the lines and edges created by the grass window's light."
Additional Information: All three doors open easily, with no trouble. This is the first puzzle the players encountered which was truly dangerous, as two of the doors led to particularly deadly traps, the natures of which are not important to the puzzle. If the characters examine the area of distorted light, they will notice that the lines & edges of the light form the word "look" in common. Directing the lens toward the doors will identify them either as "Death" or "Forward."
Intended Solution: To go through the door which reads "Forward" when the light is directed at it.
What They Did: I must confess, my memory is somewhat fuzzy on precisely how this final puzzle played out. I do recall that they were somewhat confused by the lens at first, but they did notice that it said "look." (I allowed them a passive perception check to notice it.) After that they made the leap to directing the lens at the doors, and found the correct way out easily. The entire process was brief, perhaps 2-4 minutes.
I view all four of these puzzles as successes. The players enjoyed themselves, and had some good discussion about what solutions they should attempt. Up until that point, these players had participated in sessions which focused on exploration and combat, so it was a good way to give them a new type of challenge. As mentioned before, setting up a good puzzle can be extremely difficult, so it's important to proceed with caution if you're planning to use one. While hardly exhaustive, I find these tips very useful in designing my puzzles.
- Puzzles should almost never be required for progression through the adventure, and if they are, they should be easier than normal. You might notice that the four above puzzles were in fact required for progression, since the characters were after the illusionist for help. But neither were any of them particularly difficult to sole, and I was flexible with my solutions. If you do make solving a puzzle a necessary, then you risk the players becoming stuck. And if they get stuck, the GM is left with two options. One, the GM can give them out-of-character help, or somehow allow them to bypass the puzzle. This steals player agency, and makes players feel as though they're being railroaded. The other option is simply to allow them to remain stuck for as long as it takes, even long after they've lost interest. Both responses suck the fun out of a game. Since the GM is the fun facilitator (or the funcilitator!), sucking the fun out of a game is a pretty severe failure of GMing.
- Make sure there are clear hints to help players succeed. Looking at the puzzles above, the first one had the four leaf clovers, the second had its conditions spelled out, and the fourth had the spot of light which formed the word "look." Only the third puzzle lacked a clear hint, and that was the puzzle which stymied the players longest.
- Allow "half solutions" which help the players get there. If the players try something that doesn't work, they'll rarely attempt subtle permutations of what they've already tried. So if they attempt a solution which is close to the answer, but not quite, then after they fail they're likely to try something completely different, rather than try something similar to what has already not worked. If the solution your players come up with is near the mark, give them some indication of that. If it's a door they're trying to open, have the door open just a crack, but no further. In the first puzzle above, I would have allowed players to have some success by putting the clovers on their feet, even though this was not the "correct" answer.
- What is obvious to you as the designer of the puzzle will never be as obvious to the players as those challenged by the puzzle. This rule is absolute. Err on the side of caution. It's better that your puzzles be too easy, than too hard.
- In order to help with that previous point, confer with a third party before the game. Asking a friend who won't be playing in the game to solve your puzzle will give you a better sense of what works and what doesn't.