Moon is a FPS developed by Renegade Kid and released in 2009 for the Nintendo DS, but originally the project was born as a 2D side-scrolling action adventure for the GameBoy Color. Moon GBC was revealed by Jools Watsham, game director at Renegade Kid, in a video from his Youtube Channel.
The GameBoy Color version of Moon was never released, but the scenario and the characters were later reused to create the DS version. Moon looked like an interesting adventure, similar to Metroid II, and it’s sad that it did not had its chance on the GameBoy Color.
Props to Jools Watsham for sharing these screens from the prototype!
Thanks to Celine for the contribution!
Videos (he talks about Moon GBC @ 3:30):
For comparison, here’s the DS version: