Downwell
Developed by Moppin
About the game — TGN editorial note
Downwell is a vertically scrolling roguelike shooter and platformer with underground levels, drawn in a four-color palette that picks out gems, enemies and key items in red against black and white. Extra palettes can be unlocked to change those colors. It was made solely by Ojiro Fumoto under the Moppin name in Japan using GameMaker, and Devolver Digital published it in October 2015.