Like Sonic Mania? Like Knuckles Chaotix? Like both games? Then this is the SAGE mod for you. Chaotix Mania "will attempt to remake the game, Knuckles Chaotix, into Sonic Mania". You don't have to worry about dragging a partner character around with any ring bonding, and there's no roulette wheel to randomly decide the level you'll play, so you don't need to worry abou any of that.
The SAGE demo has 7 levels, along with Mania and Encore versions. The stages are also not direct ports, but remade level designs to make it so a single player can complete them. There are also new music tracks, badniks, and much more. The Special Stages even received a new look. So, if you're interested, go download it here.