Battle your way through a dungeon, then upgrade and unlock new gear (Like the "Satanic Blade," a giant sword that burns enemies or a staff that launches lasers to kill a whole line of slimes at once) by spending your life at a demonic altar which also re-colors the entire game, and then enter the next dungeon, with stronger, faster, and deadlier enemies, battling your way from the first demonic red dungeon to an acid-green dungeon all the way to the final glowing white dungeons.
https://www.youtube.com/watch?v=4wqyXQlQ4I

The tutorial text could have used a background to be better readable, and I would have wished for some different enemies after a while.
But in total it is a really solid entry!
This game was fun, the audio was good, the mood was properly atmospheric for a dark hellscape, and the theme was well represented.
I'd count that as quite a successful game! Good job!