One of the largest projects that proudly represents the fandom mods is FNF Indie Cross. It takes characters from popular independent creations, and your first opponents will be Cuphead, Sans, and Ink Bendy. This feels a lot like a boss fight, given professionally created compositions in the OST fashion and vibing graphical styles unique for each boss.
As you proceed, the song gradually goes the wrong way. Bad notes appear that bite off your health as you click them. However, the loser’s screen is another piece of art you would want to spectate.