Retro-style 2D scrolling platform shooter

Dave Gnukem is a retro-style 2D scrolling platform shooter similar to, and inspired by, Duke Nukem 1 (~1991).
While the original Duke Nukem 1 had 16-color EGA 320x200 graphics; the aim here is 'similar but different' gameplay and 'look and feel'.
It is kind of a parody of the original.
Please note it is not a 'clone', and not a 're-make'.