Knit bones, stitch muscles, and weave neurons into biologically-realistic underwater lifeforms.
It's like Spore, but with actual science.
Liked the cell stage of Spore, but wanted more depth? Gotten merrily lost in the graphical programming puzzles of SpaceChem? Love the "can I manage to build this...?" creativity of Kerbal Space Program?
Crescent Loom is the very first biologically-realistic nervous system simulation game. It lets you — in a hands-on, mad-scientist way — tinker with everything from neurotransmitter to the ecological niche of an animal.
So dive in and maybe — just maybe — by poking around with these simple creatures you'll figure something out about how your own body ticks.
Crescent Loom is in open development; expect major bugs, crashes, changes, and additions as I work on it over the next few years.
The best way to keep an eye on this is by subscribing to wickletter.
You can share creatures you create on the reddit.
The "play online free" link above brings you to the HTML5 version that runs in-browser. Paying for Crescent Loom lets you download a version that runs natively on PC/Mac/Linux. The only differences are the technical constraints; HTML5 has no saving/loading locally, runs slower, and is locked to a 1024x768 resolution.