I've gone up to 50 generations with a creature that seems pretty simple and functional, but they aren't making any progress forward. Is the goal in this mode only to hold on?

Well, holding on is better than falling but the creatures have to be able to actively climb up to get a fitness score above 50%.

Here's one made by user Mr. No Name on a japanese forum: http://imgur.com/dp6ApTZ

Here's another great one by kwanasp on reddit: https://gfycat.com/ClearcutDelightfulErmine

Thanks, Keiwan. I guess I'll improve my design and give it a lot more time.

Some creatures i got to climb.