Binding of Isaac dev rejects writing "safe" things, discusses new "breeding sim"

I can't say I expected to be writing about eugenics when I woke up this morning, but the gaming news cycle always throws up a few surprises. Mewgenics is a game that designer and artist Edmund McMillen describes as a "randomly generated turn-based strategy game where there's cats." With "breeding sim" elements and plenty of The Binding of Isaac DNA, this is a systemic game that's not for the faint-hearted. But a new interview reveals that six years of development have produced a surprisingly touching response from fans.

The idea for Mewgenics was spawned from buying real cats. McMillen's wife loves rare breeds, but they come with all sorts of health problems thanks to regimes that force certain traits - traits that are desirable to owners but are often dangerous for the animals themselves. Combining this with his own upbringing led McMillen to think about breeding, and eugenics, as a game mechanic.

"We just added ADHD, which raises your intelligence and your speed, but you've got five seconds to make an action or [the cat] just does something, it defaults to something else," he explains to indie documentary channel NoClip_2. 

"Autism lowers the charisma, raises the intelligence, and then it makes all the things that the cat is naturally born with, they're good at. So they're really good at these one or two specific things, but everything else is harder."

McMillen draws on his own experiences here, acknowledging that his obsessive thinking turned to game design and his hyperactivity was channeled creatively. You can see his background in Newgrounds flash games about dressing up dead babies shine through here, but he now seems to be approaching these topics with a bit more maturity.

Design-wise, he says it's important that there's a "silver lining" to all of these traits, to the point where his nephew, who has rigorously playtested the game, created an incredible run by breeding all his cats to have cancer, which slowly damages their health but also triggers random and sometimes powerful mutations. Through selective breeding, his 'cancer run' powered him through the game. 

This is more than just shock value. It's a deep system with thousands of possible permutations, but McMillen says that many neurodivergent players also see the cats in Mewgenics as positive representation. 

"There was some worry (not by me)," he explains, "That this could come out wrong, that people would think that I'm mocking whatever, so I tested the waters." The resulting social media posts went viral. "It feels like representation, too," he says. "Which is really neat, because it wasn't necessarily intended as such. It was just akin to, 'I have these disorders. I pass these disorders to my kids. This is going to make their lives in this world, in this generalized society, harder. But, there are things that they'll be better at'."

He's not shying away from difficult topics and, as long as it doesn't punch down, I don't mind it either. "The Binding of Isaac is a game about child abuse," he continues. "You don't need to constantly just write about things that are safe. There's more going on here, I promise."

Mewgenics will release on Tuesday, February 10, 2026. You can find it on Steam here.

If you're interested in eugenics, seek help immediately. But if you're interested in it as a game mechanic, check out our list of the best indie games for boundary-pushing designs that triple-A developers wouldn't dare implement. The best roguelike games will also tickle that systemic itch.

What do you make of Mewgenics' systems? Let us know in our community Discord server, where readers and staff share photos of their IRL cats. Or we should.