Here are the formulas responsible for calculating damage and stuff. $userlevel$ refers to the level rounded down to the nearest integer.
Consult the Type Charts for info on the modifiers. Places have a max of 100 health.
$ damage = userlevel ^ {0.5} * 4 * typemod * terrainmod * weathermod $
$ recoil = userlevel ^ {0.5} * 5 $
Level is stored as a number with a bunch of decimal places. A fraction of a level is added for every action taken. That fraction is calculated as follows:
$ levelfrac = ((userlevel + 1) ^ 2) ^ {-1.2} $
The max user health is very simple:
$ health = userlevel * 100 $