Among the other libraries, another very useful one is the Open Dynamics Engine (ODE), a library devoted to the simulation of rigid body physics. It's obvious that such a library is very useful in a game, because realistic physics behaviors in the bodies that surround the player is a strong requirement nowadays.
As usual APOCALYX defines a Lua interface to the ODE functions, so the script writer can easily access their powerful capabilities. There are also very simple scripts, such as "BouncingBall.lua" and "BallsOnTriMesh.lua" in DemoPack1, that show how to call some of the simplest functions ans set up a simple environment.
The author describes the library as follows: "The Open Dynamics Engine (ODE) is a free, industrial quality library for simulating articulated rigid body dynamics. For example, it is good for simulating ground vehicles, legged creatures, and moving objects in VR environments. It is fast, flexible and robust, and it has built-in collision detection."