Boston Dynamics’ is one of the world’s leading robotics companies. Its long been famous for its increasingly advanced four-legged robot “dogs” bomb squads are already deploying. But I was today years old when I learned that the company also makes a humanoid robot so darn advanced it can do a backflip. And I’ll be honest, it creeps me out a bit.

First of all, Boston Dynamics’ little four-legged robot helper has the cute name “spot.” What’s not to love? But its huge humanoid model is called “Atlas.” That name’s a little spot on, if you ask me. In a video two years ago called “Partners in Parkour” (embedded below), Boston Dynamics revealed that Atlas can do all kinds of cool tricks. Including a backflip for goodness sake!

So how does this robot pull its moves off? And does it make you feel a bit uncomfortable too?

Boston Dynamics is slightly vague about Atlas’ precise dimensions. They list its height as 1.5 meters, which would be just under five feet. It weighs in at 196 pounds. And before you call this bot big-boned, know that the makers 3D-printed a ton of aluminum and titanium components to get the strength-to-weight ratio down. Atlas has 28 separate hydraulic joints, and those are hefty. But overall, it can run 5.5 mph.

Why worry about a humanoid robot’s strength-to-weight ratio? So the software team could push the bounds of what a humanoid robot could do. I still think of humanoid robots in terms of Honda’s Asimo, which just shuffled around. But Atlas uses an entirely new paradigm of perceptive movement.

This means that instead of performing a series of pre-programed moves, the engineers are attempting to teach it to react and adjust. In demonstrations, you can see Atlas trip and catch itself. If the engineers ask it to do a backflip and then a fist-pump, it might stumble a bit in ways it doesn’t when it just does the fist-pump alone. But it is learning. Its directions look less like “Open your left hand, pickup that bag…” and more like “Move that bag from here to here. You figure out how.”

Early on, Boston Dynamics had much more luck with a four-legged walking robot than a humanoid one on two legs. Its engineers admit the humanoid form factor poses a ton of challenges. And the result may not be the most useful: A bigger robot, even if it isn’t as nimble, would be better at industrial tasks. A smaller, nimbler robot–such as spot–is a more useful remote drone for bomb squads or building inspectors or search-and-rescue teams. Most things a humanoid robot can do, well a human can do it too.

“Humanoids are interesting from a couple perspectives…First, they capture our vision of a go-anywhere, do-anything robot of the future. They may not be the best design for any particular task, but if you wanted to build one platform that could perform a wide variety of physical tasks, we already know that a human form factor is capable of doing that.”

 Scott Kuindersma, the Atlas team lead at Boston Dynamics

I can certainly see the technical benefits of a humanoid robot. Even if we are decades away from a “go-anywhere, do-anything” bot that can interact with all aspects of human life. But I find them the creepiest. I see a big industrial robot, even on autopilot, and I know I could easily outrun it. I see a cute little four-legged robot like “spot” and I imagine I could eventually kick it over. But Atlas is something else entirely.

I’m not the first person to feel icky about humanoid robots. Professor Massahiro Mori introduced the term “uncanny valley” in 1970. Its a psychological principle predicting that a robot very much unlike a human won’t bother us at all. Think R2D2 or Wall-E. But the more like us a robot is, the more uncomfortable it will make us. The phrase “valley” suggests that at some point, a robot identical to a human in every way would no longer make us uncomfortable. Is that true? I’m not sure, but something tells me we’ll find out eventually.

Next, read about the robot dog that sacrificed itself to save police officers, or see if YouTuber Cleo Abram can beat Atlas in a jousting mach in the video below: