Underlying implementation is a pure rendering engine, network and some low level core stuff (which is, as I mentioned a facelifted quake1 engine). All game logic including weapons, enemies, ai, bullet and explosion raytracing and game objects called 'entities' are contained in SDK and being compiled to client.dll and server.dll for server side and client side respectively. What derefr is talking about I have no idea because it has not a slightest relation to the game (no offense)