Thursday, February 16, 2012

Procedurally generated puzzles

Just jotting down some informal thoughts on types of puzzles and how to proceduraly generate them. Each puzzle is really a barrier that you must overcome to get to the other side. Place a puzzle when you need a barrier to seperate zones, protect treasure, or just to keep things interesting.

Minigames. Reminds me of the Wii party games where whichever team gets the best overall score after 5 events wins the tournament. Slider puzzles, tower of hanoi, checkers, gambling, etc. It would take time to code each one but it would also break up the monotony. You could also make the real game a metagame of the minigames. Imagine everyone in the game is obsessed with a collectable card game. By finding new cards in the game world you improve your chances of winning the card minigame, which could lead to rewards that improve your chances of the real game. Done right it would be interesting and fun diversion; done wrongly it would be a tedious and required waste of time.

(days later) I just remembered that Star Wars: Knights Of The Old Republic had this with Pazaak! I was thinking more along the lines of a Magic The Gathering type minigame, but a poker-blackjack hybrid is a good idea too. Neat! Proof that my idea works!

Logic mazes. Reminds me of many games where you have to move like a knight on a giant chess board or slide across the ice in just the right pattern to make it to the other side. For these puzzles you must go from here to there but you must follow a certain way of moving. I think these would be easier to make in reverse. For example, start with an impassible expanse of ice. Start at the end point. Pick a direction and place a block in that neighboring cell. Move the opposite direction a few spaces. Repeat several times, making sure not to place blocks in areas the player will need to later pass through, and you end up with an end point, a start point, and at least one way to move from the start to the end. There are many more examples of logic mazes at

Inventory based. Reminds me of Metroidvania games. You must have a certain item or ability in order to pass. A locked door requires a key, a hall of spikes requires the spike armor, cracked walls require bombs. Basically there's some sort of "lock" and some sort of inventory "key" is required to pass. To place an inventory based puzzle, simply pick something from a preset table of a "lock" and item "key" and place the key somewhere before the lock. Or pick a random item from the world as the key: "The burly guard won't let you pass until you give him A HAM SANDWICH."

Knowledge based. Reminds me of Myst. You must answer a question or enter the correct sequence to pass. A combination lock where the randomized combination is written down elsewhere or a guard who asks you questions that you would only know from reading books in the game or talking to people in the game. Like the inventory puzzles, simply pick something from a preset table of a "lock" and an information "key" and place the randomly generated key somewhere before the lock.

Environment based. Reminds me of many sub puzzles in modern Zelda games. You must change the environment to a certain state before you can pass. Pull the lever to open a door, push all 4 buttons to lower the bridge, set all 6 torches on fire to open the treasure chest, redirect the laser to destroy the statue. This could be a superset of sokoban puzzles which are really just "push the blocks into the marked places". If you look at it a certain way, the requirements or triggers could even involve other people or groups: the king must be dead, the mages guild must be at war with the fighters guild, the price of milk must be low, the senate must be mostly of the Merchant's Alliance, etc.

These puzzles can be combined to form larger and more intricate puzzles:

To get the treasure chest you must push all four buttons
  • to push button 1 you just walk over and push it
  • to push button 2 you must cross a bottomless pit
    • to cross the pit you must purchace Flying Boots or know how to teleport
  • to push button 3 you must open the giant door
    • to open the door you must find and reassemble the 2 gears to the door machinery
      • gear 1 is on the other side of a giant randomized sokoban puzzle
      • gear 2 is buried at a random location
        • shovels can be purchaced at stores
        • the location is on a map you find in the dungeon
      • reassembling the gears is a slider puzzle
  • to push button 4 you must defeat the guardian with a special sword and a special shield 
    • to get the special sword you must help the dying king
      • the king will give you the sword if you give him an elixer of life that no one knows how to make
        • the recipe is randomly generated but written in a recipie book - or you could just start mixing things and get lucky
    • to get the special shield you must play the specific melody on the piano
      • the notes of the randomized melody are written on the wall of another room
You could create a puzzle like this at each dungeon or important location or create one giant puzzle that includes all the major locations in the game world.

Ideas like this aren't worth much unless actually implemented though. I'll have to create some proof of concept or even a roguelike that has puzzles like this in it. One of these days.

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