Correlated randomness in Slay the Spire 2

6 hours ago

Slay the Spire 2 has a bug called correlated randomness (CRNG), where different random number generators share linear relationships.
This causes predictable patterns, like Neow's Bones having a ~54% chance of giving Debt in Underdocks.
Some outcomes are impossible, such as getting Rebound from the Trash Heap event.
Potion drop rates vary widely: 76% in Underdocks vs. 4% in Overgrowth for the first fight.
Many in-game events and relics show biased distributions due to CRNG, impacting gameplay and balance.
The issue stems from C#'s System.Random algorithm initializing RNGs with seeds that differ linearly.
Fixing CRNG is straightforward, such as replacing System.Random with a non-linear PRNG.
The bug was discovered accidentally while searching for specific seeds, revealing unexpected correlations.

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