there are 4 groups of keys: special, general, player control and camera control.

special key is hard coded in and not maped in the input file 
(mostly mapped to the special keys on the keyboard, not shareable)

same key can be maped to a function in more than one group, but not to more than one function with in a group
and when they are shared like that, all shared functions will be excuted (in the above order)

player control and camera control keys can also be shared exclusivly if you enable toggle
meaning if toggle is set to player, then player function of the mapping will be called, vise versa
toggle is useful for 2 player mode, when there is not enough keys to go around

player control keys and camera control keys wil be repeated if they are held down
so becareful if you share control keys with special/general keys

control keys should not be shared between players, only player 0 will be called