Mutant Mudds is a 2d platformer developed by Renegade Kid and released for 3DS and PC in 2012. Originally, as you can see from the video and the screenshots below, the game was going to be a 3D third-person shooter. A short demo made in two weeks that used a modified version of Moon engine was in fact shown to IGN at e3 2009.
However, Renegade Kid didn’t succeed in finding a publisher, and so they tried to release it on DSiWare in 2010. That failed too, but in 2011 the developers transformed Mutant Mudds in a 2D side-scroller and decided to publish it themselves on the 3DS eshop.