Ability to push things around

[sunjay]

It would be neat if the player could push stone blocks around and stuff. Would require changing the physics engine to accept a mass with each colliding bounding box. We would then only apply a fraction of the full force required to separate the two intersecting rectangles. This force would be proportional to the ratio of their masses.

This requires doing two passes over the objects since the first pass will push some objects halfway and then the second pass will need to push other objects the rest of the way.