Principia

Principia is, in its simplest form, a physics-based sandbox game. In Principia, you can build contraptions and simulate them in the physics simulation. This could be a mechanical contraption, an RC car, or a pinball game. Principia also contains a LuaScript object which allows you to write and create Lua programs that can interact with and affect the simulation.

Principia also features the Adventure game mode. In this game mode, you take control of a small robot which can do whatever you decide it to do. It can take part in a giant battle with enemy robots, or it can take control of the giant robot and wreak havoc on the world.

History
Principia was the successor to a previous 2011 mobile game by Bithack AB called Apparatus. It was released as a proprietary paid game in November 2013 for Android, and later for Windows and iOS. The development was abandoned shortly after version 1.5.1 released in October 2014, due to financial difficulties.

In April 2016, Bithack announced that Principia would be made open source under the BSD 3-Clause license, however this fell through. It wasn't until in August 2022 that Principia's source code was finally released onto GitHub, and it is now being further developed as a community project.