Luanti
A free open-source platform for building and playing blocky voxel games, formerly called Minetest, widely used in schools.
Luanti is an open-source game engine and platform for voxel games, meaning games built out of a grid of cubes. It started in 2010 under the name Minetest, inspired by early Minecraft but written to run well on modest hardware, and was renamed Luanti in 2024. It ships with no game of its own. Players pick from a community catalogue, and anyone can write their own game using its Lua scripting interface.
The project matters beyond gaming because it is free, modifiable and offline-capable, which made it popular in schools across Europe as a way to teach programming. It has also become an unwilling test case for automated copyright enforcement: its Android app has repeatedly been pulled from Google Play over DMCA notices claiming it copies Minecraft, which it does not.