I'm playing with this for quite a while. It's a very interresting and addictive game! I even took the time to test some already existing schematics in nature (like the horse or the cheetah) to be able to compare with real life (the most it can be done hehe). I'll summarise what kind of things that could be improved from this version for a second version (can't wait to see that!!).
The first thing that I noticed is that the friction is too high. We can easily see it when a creature trying to make a foward trust or climb the stairs. Legs easily slip, even if we make feline legs and add some fangs.
Next thing I noticed is that the creature always tries to do the task right away, rather than trying to stand without falling first (reaching equilibrium).
For the task of climbing, the software doesn't care about the space the creature is taking, and can make joints appear through the ground, so making the creature bug instantly. The hill could also have stairs a little more large. Or maybe making the creature start on a flat ground.