For robots, bi-pedal locomotion is tough business. Now, imagine adding some stairs into the mix and taking away the ability to actually see where they’re walking.

That’s exactly the challenge researchers at Oregon State University set up for their robot, Cassie, made by Agility Robotics. And rather than having us tell you how Cassie performed, just watch this video of it tackling this formidable test for yourself.

Equally impressive as Cassie’s ability to traverse stairs by feel and memory alone is the method by which researchers trained the robot.

Instead of having Cassie undergo a potentially dangerous crash course via actually climbing stairs, they used a method called sim-to-real Reinforcement Learning, which trained the bot virtually, allowing it to make mistakes without taking any IRL spills.

Researchers say there’s still room for growth in Cassie’s performance. For instance, the bot could only walk at standard speed without faltering... and it isn’t particularly good at improvising.