Space Mutants 2 is currently in development! I have no idea when it will be complete, but things are rolling along nicely. This time around the game play experience will take a turn from being a linear playthrough to a more pf an open and explorable world. Think Metroid on the NES. Of course I will release it free of charge once it is complete. I'd rather the people play it than for it to just sit on the shelf and collect dust, lol. It will have all of the old monsters and bosses plus an additional 13 new enemy types! If you'd like to follow along with the development of this upcoming Space Mutants 2 release, here is the link to it's development page.
https://www.nesmakers.com/index.php?threads/space-mutants-2.8935/#post-52942