Sloths aren't the most exciting creatures to inspire a Lego creation, but 222Doc has left us thoroughly impressed with this quadra-ped robot called X-4 that's able to autonomously climb a ladder—even when inverted.

Surprisingly, it's powered by just a single Mindstorms NXT that controls eight servo motors, four smaller Lego motors, and a set of four sensors. And while it's as slow as a sloth—if not slower—that just makes the attention to detail and accuracy here all the more impressive. [222Doc's Blogspace via Make]