The source code of the 2007 PC game S.T.A.L.K.E.R.: Shadow of Chernobyl leaked in 2010. I decided to use it to fix a few problems with the game.
%APPDATA%\s.t.a.l.k.e.r. - shadow of chernobyl
C:\s.t.a.l.k.e.r. - shadow of chernobyl
Various snapshots I have taken of my experiments (newest first). For more details, read this thread.