Objects and ennemies

The interactive elements of the game can be classified in 3 categories :
 * 1) The neutral entities : Those objects don't have a will of their own, and won't fire on someone in particular
 * 2) The aggressive entities : Those being can track a player and fire with precision. Upon damage or sight.
 * 3) The item entities : Those are the item that can be destroyed to gain a bonus or malus.