Project

Minecraft TNT Mod

· Updated

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Overview

This is my first Minecraft mod, built for Java Edition 1.21.5. I kept the scope simple: add 3 new types of TNT, each with a different explosion behaviour.

Architecture

The key insight I picked up early: in Minecraft, a TNT block and a primed TNT are two separate things. When you ignite a TntBlock, it spawns a PrimedTnt entity, that entity is what actually has physics and triggers the explosion.

So for each custom TNT type I followed the same pattern:

  • A *TntBlock extending TntBlock, whose only job is to spawn the matching primed entity.
  • A *TntEntity extending PrimedTnt, where I override explode() to change the behaviour.

The 3 Types

Water TNT - runs a triple nested loop around the explosion center and replaces every block (air included) with water source blocks, creating a sudden flood in a cubic radius.

Water TNT

Slime TNT - same loop logic, but skips air blocks and replaces solid blocks with slime blocks, turning the terrain into a bouncy mess.

Slime TNT

BOOM TNT - a much larger explosion that spawns several PrimedTnt entities and immediately detonates them. The chain reaction takes about 2 minutes to fully resolve, and the result is exactly what you’d expect haha. (I also do a cleanup after the explosion, which is why the result looks so round and clean.)

BOOM TNT

What I learned

  • The block/entity split in Minecraft’s TNT system, and how to hook into it cleanly through inheritance.
  • How to override explode() to fully control explosion behaviour without touching vanilla code.
  • Keeping custom entity registration and block spawning in sync, WaterTntBlock must spawn WaterTntEntity, not the vanilla PrimedTnt.
  • Blocks and items are registered separately, a TNT block needs both a block registration and an item registration to be placeable and obtainable in-game.