The platformers can be purchased separately — the first two for $2.99 each, and Manhattan Project for $5.99 — or in a bundle, the Duke Nukem Platformer Pack, for $9.99. Manhattan Project has been updated for widescreen displays and with "partial controller support," and all three games support Steam Play across Windows PC and Mac.
Apogee Software (now 3D Realms) released the original Duke Nukem on MS-DOS in 1991, and launched a sequel in 1993 that was ported to iOS this year. Manhattan Project was developed by an outside studio, Sunstorm Interactive, and was published by the now-defunct Arush Entertainment in 2002. Microsoft Game Studios published the Xbox Live Arcade port of the game, which was released in 2010.
You can watch a trailer for the Duke Nukem Platformer Pack above.