BOOM

BOOM, one of the first Doom source ports, is TeamTNT's special version of Doom that removed many mapping limitations (the dreaded VPO and so on), fixed recurring bugs, and added extended functionality such as generalized LineDef action types and features such as new HUDs to the game. ZDoom supports nearly all of BOOM's editing features.

BOOM has since been ported to Windows and Linux, most notably in the form of PrBoom.