Reactive World

The mod tracks kills made by players in the Overworld, counting each tracked species separately. Every kill raises that species' count by 1, and the game notes the moment of the latest kill. When a tracked mob tries to spawn naturally, the mod calculates a probability from the count using an S-curve function, and that probability decides whether the spawn is cancelled. A low count leaves spawns almost unaffected, a count around the midpoint cancels about half of them, and a high count suppresses nearly all of them.

The count does not stay high on its own. Once a species has not been hunted recently, a periodic timer applies a regeneration formula, and the count drops slowly, so populations recover. Stopping for several in-game days lets natural spawn rates return over time, and a count below 1 resets to zero. Farmland also follows a related rule: a player's harvest does not turn the soil back to dirt until the land is exhausted, while an automatic system converts it only at maximum exhaustion, and a green particle effect shows the land recovering during a fallow period.

Reactive World requires NeoForge, and the mod is not open source. It is published for NeoForge only, with one game version, 26.1.2. The environment is client and server, so the server and every player need the mod, and the settings are adjusted in the Minecraft configuration screen.