I know a few people on my friends list have been playing Don't Starve (a cute survival game it's all too easy to die in). Niche takes that idea and adds breeding/genetics to it. Only the demo is out now (free download), but even just that is lots of fun -- I've played it five times in a row.
It's really quite cute, both the graphics and the minimal sounds.
You breed new creatures (if you're lucky) and use points you earn to improve their genes.
It's quite fun, and at least in my experience thus far, is as challenging to survive as Don't Starve is.