My thoughts on the games
Rat World:
It's a basic grindfest. Kill rat, try not to die, repeat until you either are one-shotting the swarms or you die to attrition. It's basic, would be better if there was more to it, but I think it did what you intended.
Rat World Ace:
There's a little more to this one. Greater skill variety gives the battles a little more depth (not much, but it's something) and there's even some variation in enemies! Player guidance is lacking - I never found the town or the final boss - but I appreciate that this one is a little more fleshed-out than the previous iteration.