Sacrificing a particular gun/card will grant you a special move, from an extra jump to a burst of smashing speed, to help you traverse the hazardous terrain.
I don’t know how to describe this game, and watching the video above is probably only marginally helpful. But basically, you are an undead demon assassin guy and you have to make your way through hundreds of precariously designed levels as quickly as possible by using the powers granted to you by a mountain of weapons, which you activate by burning through a deck of playing cards, in the hopes of winning a place in heaven. Sacrificing a particular gun/card will grant you a special move, from an extra jump to a burst of smashing speed, to help you traverse the hazardous terrain. The point is to finish as fast as you can. No, I don’t understand it either, and I’ve already played it. But once you’ve oriented yourself, it’s a good time—and the story is fun too.