The devil lost his favorite marble.
Well not “lost” it so much as he ate it.
Point is he wants his marble back and it’s your job to go get it. His intestines are windy with many passages and you’re likely to get lost; you’re not the first person he sent in. Use your lantern to find your way, but don’t run out of fuel or you’ll be lost forever. Be ware of partially digested meals wandering the devil’s tract. Keep an eye out for friendly spirits, you can capture them in your lantern and burn them for light.
WASD to move, mouse to aim the lantern, and Esc to reset.