Behind the Scenes on Retrofitting Dungeon Crawl Stone Soup’s Random Seeding

If you’re not familiar with this idea from other games with random procedural generation like Minecraft, Spelunky and brogue, here’s how it’s supposed to work: if you enter a specific code (the “seed”) into the game when starting it, you’ll get a repeatable form of randomness that encompasses dungeon layout, items, and monsters. You can think of the RNG as, given a seed, providing a “code book” of integers that acts random, but as long as you have the code book and the correct rules/constraints (giving you position in the list), you can decode the behavior of the game. Not only that, this first assumption wasn’t made: DCSS before 0.23 used a single RNG for gameplay and levelgen decisions, so any different action the player took might lead to completely different level generation.

Source: crawl.develz.org