I ran my idea, a top-down, sci-fi roguelike bullet-hell shooter that swaps Enter the Gungeon's gun mythology for modular weapon crafting and gravity-bending combat through the game validator.
It suggested it was unreasonable in two weeks, which I thought would be the case, and I was trying to mix too many genres. It suggested beginng with building one arena with three modular parts and one gravity mechanic. See if that core loop is actually fun before building a whole roguelike.
Fun factor 7.5.
Next move, prepring the correct prompt or promps