Combination Locks

Either a door or a locked container may have a combination lock instead of a physical key. The most straightforward type of combination lock puzzle is, perhaps literally, a combination lock. It may have a single dial that needs to be turned to three or four numbers in succession, or a row of dials each of which needs to be set to a specific number. The number of possible combinations is likely to be large, so the only practical way to solve the puzzle is to find the piece of paper on which some thoughtful or absent-minded person has scribbled down the combination.

A more interesting combination lock puzzle can be created by scattering clues around. For instance, the dials might be of various colors, and each dial might have a number of symbols on it. Somewhere in the model world you might find the color red associated with a bird, which would be a clue that the red dial should be turned to the bird symbol. (“Blue Lacuna,” by Aaron Reed, has a puzzle of this type.)

Large mechanisms such as revolving rooms can operate as combination locks: To use one or more of the exits from the room, you’ll need to figure out how the buttons and levers change the orientation of the room. In another variant, the buttons and levers might not be in the same room as the lock mechanism itself: To solve the puzzle, you may need to travel from room to room to see what happened when you moved the lever.

In a more general sense, any puzzle that requires the player to perform two or more actions in a specific order qualifies as a combination lock. If the game includes a muzzle-loading rifle, for instance, the player will need to pour the powder into the barrel, place a patch on the end of the barrel, put the ball in the patch, and then use the ramrod to push the ball and patch down into the barrel. If the player puts the bullet into the barrel first and then the powder, the rifle won’t fire. (The real procedure also requires measuring the powder, tapping the stock against the ground to settle the powder, and using a bullet starter before the ramrod to get the ball started down the barrel. But that may be too much detail for a game.)