Physics

The soccer field and all objects on it are 2-dimensional. There is no notion of height on any object.
The players and the ball are treated as circles. All distances and angles used and reported are to the centers of the circles. The action model is discrete
All objects move according to Newtonian physics. They have a decay. Move and Kick operations are implemented as vector additions to the current velocity vector.
If at the end of the simulation cycle, two objects overlap, then the objects are moved back until they do not overlap.
Noise is added to the movement of objects.