RigelEngine is a re-implementation of the game Duke Nukem II, originally released by Apogee Software in 1993 for MS-DOS. It works as a drop-in replacement for the original executable: It reads the game's data files and plays just like the original, but runs natively on modern operating systems. On top of that, it offers various modern enhancements like higher frame rate, better game controller support, a wide-screen mode, quick saving etc.

In order to run RigelEngine, the game data from the original game is required. Both the shareware version and the registered version work.

You can grab the shareware version from archive.org: https://archive.org/download/msdos_DUKE2_shareware/DUKE2.zip