Requires the "GZDOOM"-engine (included), and a copy of "DOOM II: Hell On Earth" (sold separately). Installation & Play (1) Unpack the download to obtain the "NGX01A1" folder (2) Make an extra copy of your "DOOM2.WAD" file into this folder (3) Drag & Drop "NGX01A1.PK3" onto "GZDOOM.EXE" to play.