Gravy Tea is the name of the smog heap engine for games based on gravity and orbital mechanics. It is able to represent a very simple view of a solar system and animate the bodies in that solar system.
Unstable is a game based on the Gravy Tea engine.
In this game the user is presented with an unstable solar system, which they must fix in order to progress to the next level.
Rubber Rockets is a game based on the Gravy Tea engine.
In this game the user controls a rocket that has an infinite amount of fuel. Each level presents a new goal that the user must accomplish, such as getting into orbit or transferring from one planet to another.