Jammer Hearts will (hopefully) be a Flailsnails-compatible setting based mostly on the universe of Kingdom Hearts with a generous helping of Spelljammer to round it out. I'm using mostly Labyrinth Lord Advanced Rules and 2nd Edition AD&D to form the base of the rules set, with some help from Lamentations of the Flame Princess (namely, for how summoning heartless works)
Jammer Hearts is meant to be a ridiculous pulp action adventure game about THE POWER OF FRIENDSHIP but also IN SPAAAAACE where everything is possible and Rule of Cool wins the day. Will it be deadly? Well yes, probably. Will it be ridiculous? Dude it's Flailsnails, we have cowboys and robots and Castlevania and fucking cake golems already, it'll be really hard for me to make this more ridiculous than it already is.
Jammer Hearts will have room for just about everything if you can make an excuse for it existing. I'll figure out exactly what system it'll be based on later but in all honesty it's probably "If it's 2nd ed AD&D and earlier OR an OSR compatible system, it probably exists in a Crystal Sphere somewhere." ANYTHING can be from this universe. We are talking about two base systems where this was explicitly true.
Coincidentally this also gives me a convenient excuse to have other Flailsnails characters show up (WILDSPACE!) and other GMs can steal my stuff (... WILDSPACE)
I have never designed a campaign setting before god help me.