[horsa]

By "game editing" do you mean altering/moding the game files ?

A lot of the relevant files are text files and can be edited with a text editor like notepd or wordpad.

These include :
Udf files ( sim/units) - unit parameters
Adf, Ddf (sim/systems) - system files ( guns, ammo etc )
Dsf ( sim/dsf) - game interfaces
Tga ( sim/art/inteface/cic ) - interface art
Tga ( sim/art/textures) - clouds, sun, water, seabed ect )
Tga (sim/art/pyro ) -textures for particle effects

Also look in shell/art/interface and shell/art/dsf

Audio files are in sim/sfx

Model files are very difficult to change . For most people this means hex editing which is very difficult.
jrf (sim/models) - model files