Reactive World

A Minecraft world that remembers you.

10

Quick challenge

How far can you run before the mobs catch you?

Reactive World

Reactive World

About

Reactive World makes the Overworld's fauna react to player hunting. When you kill animals, the world remembers. The more you hunt a species, the harder it becomes for that species to naturally spawn. Leave a mob type alone long enough, and the population gradually recovers.

More features will be added over time…

Installation

* ⏩ Requires NeoForge to be installed: https://neoforged.net/. * ⏩ Copy the jar file of the mod in the "Mods" folder. * ⏩ For each version, check in the changelog the supported/tested versions of Minecraft and Neoforge.

Affected Mobs

The mod tracks kills and affects natural spawns for the following creatures:

> Bee, Axolotl, Cat, Horse, Goat, Pig, Dolphin, Camel, Frog, Llama, Rabbit, Wolf, Sheep, Mule, Ocelot, Polar Bear, Panda, Parrot, Chicken, Squid, Glow Squid, Fox, Armadillo, Tadpole, Cow, Donkey, Cod, Salmon, Tropical Fish, Pufferfish

Only kills made by players in the Overworld are counted.

How It Works

1. Kill Tracking

Every time a player kills one of the tracked mobs, the kill count for that species increases by 1. The game also records *when* the last kill happened.

2. Spawn Suppression

When a tracked mob tries to naturally spawn, the mod calculates the probability that the spawn is cancelled, using a sigmoid (S-curve) function:

$$text{cancelChance} = frac{1}{1 + e^{-(K - k_0) cdot a}}$$

| Variable | Meaning | Default | |---|---|---------| | `K` | Current kill count for that species | N/A | | `k₀` | Kill count at which there is a 50% chance a spawn is cancelled | `13` | | `a` | Steepness of the curve (how fast the penalty ramps up) | `0.4` |

- At low kill counts (well below `k₀`), spawns are almost unaffected. - At exactly `K = k₀`, 50% of natural spawns are cancelled. - At high kill counts (well above `k₀`), spawns are almost completely suppressed.

3. Fauna Regeneration

The kill count for each species slowly decreases over time, representing the population recovering. This happens on a periodic timer, but only if you haven't killed any more of that species recently.

The regeneration formula applied each interval is:

$$K_{text{new}} = K_{text{current}} times (1 - r)$$

| Variable | Meaning | Default | |---|------------------------------------------------------------------------------|---| | `r` | Regeneration rate / fraction reduced per interval | `0.02` (−2%) | | Regen interval | How often regeneration is applied | `72000` ticks (3 MC days) | | Idle threshold | Minimum time since last kill before regen triggers = `interval × multiplier` | `1.5×` → 4.5 MC days |

So if you stop killing Sheep, after 4.5 in-game days the kill counter starts dropping by 2% every 3 days, gradually restoring natural spawn rates. Once the kill count drops below 1, it is fully reset to zero.

Configuration

You can adjust these settings in the mod configuration screen from the Minecraft interface:

| Key | Description | Default | |---|---|---| | `sigmoid_k0` | Kill threshold for 50% spawn suppression | `13` | | `sigmoid_a` | Sigmoid steepness | `0.4` | | `regen_interval_ticks` | Ticks between each regen step | `72000` | | `regen_interval_multiplier` | Idle time multiplier before regen starts | `1.5` | | `regen_rate` | % of kill count removed each regen step | `0.02` |

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