Improved player and collision physics

[lschmid83]

I have already implemented a physic based system for gravity and the movement of the characters. I have received feedback from many users that jumping is too fast or not high enough that could be improved. It would be great to add new features such as climbing, wall jumps, swimming and flying, friction on surfaces for the main character and enemies. Another interesting idea would be to improve the interaction with objects in the game environment with pulleys or gears or joint types and destructing world objects. These features could be implemented using a 2D Physics engine such as Box2D. One of the biggest improvements I have been suggested is to rewrite the collision detection algorithm using bounding spheres instead of boxes.