The HoloLens is still a few years off from becoming a consumer product, but some developers are testing out the device’s gaming capabilities right now.

Ghost Invasion is a new game for Microsoft’s augmented-reality headset HoloLens, and it is out now for $1 on the Microsoft Store. Developer Appetizer Mobile, which made the stylish maze game Dim for iOS and Android, created Ghost Invasion to experiment with the AR technology that enables digital images to interact with the real-world around you. It is one of the first 100 apps for the Windows Holographic platform, and it takes advantage of many of the unique features of HoloLens.

Ghost Invasion has players fighting off waves of spirits that break through portals that appear on surfaces around you. That means the specters can rip through the walls, doors, and windows in the room you play the game in. You get to pick a weapon to keep them from overtaking you for as long as possible.

The action is similar to the HoloLens gaming demo Microsoft showed off in 2014:

Microsoft is still only selling a developer version of the HoloLens for $3,000, so Appetizer isn’t attempting to break into a huge new market. Instead, this gives the studio experience and familiarity with AR. That includes learning how to get digital game creatures and items to understand and use your real-world environment.

Ghost Invasion has the capability of doing 3D spatial mapping of rooms. It also supports spatial audio and gesture recognition. So while this game likely won’t find a massive, untapped audience, Appetizer has a head start toward understanding some of the technologies that will power any future AR and some VR software.