Ports of Keen Dreams, Catacomb 3-D and The Catacomb Abyss. The former is based on source code release coming from https://www.indiegogo.com/projects/let-s-get-keen-dreams-re-released-legally, also leading to http://steamcommunity.com/sharedfiles/filedetails/?id=315040793. The latter comes from an earlier source code release at https://github.com/FlatRockSoft/.