One player controls Kirby, the other controls Mario. Mario (famously) cannot jump, or really do much of anything. Kirby can fly, duck through the floor, and obtain Crash Powers from what appears to be an ostrich. I don’t know, I haven’t played as much Kirby as he has so I’m going with his version of events.
Code and graphics by me; lead design and additional graphics by the kid; based on original characters by Nintendo, who I hope will apprecialte that this is not really enough of a game to be worth writing cease-and-desist letters about. (I know Nintendo are very protective of their IP but I hope they will not attempt to sue a five year old child.)
The one big deviation from Kirby lore is that the kid insists on using she/her pronouns for Kirby and will not be told otherwise. This is, of course, highly problematic, but since Kirby isn’t real and never actually states a pronoun preference in any of the games, I have elected to let it slide.