A new iPhone game lets you control a character with your eyebrows. It’s mainly an experiment to use a new feature on the iPhone X camera.

Rainbrow plays a little like Frogger, albeit without any side-to-side motion controls. You simply move a character up and down between seven rows of a rainbow trying to hit stars but avoid other objects. The twist is that rather than press buttons, you frown to move down and raise your eyebrows to move up. (It’s not clear what happens if either Roger Moore or The Rock play.)

The key is the TrueDepth camera, which works along the same lines of the Kinect and is able to recognize 3D shapes. It’s what powers the facial recognition unlock feature on the iPhone X. While the technology is available for app developers, it’s previously been used mainly for gimmicks such as recreating facial expressions on an animated character.

As a security measure, third-party apps only receive a limited amount of the data the camera collects, which isn’t enough to then trigger the phone unlock.