The makers of the hit virtual reality rhythm game “Beat Saber” just released a free early build called “Beat Saber Origins” to celebrate its first anniversary.

“This build represents the game which was only one month in development and had just one temporary song,” said developer Hyperbolic Magnetism (now called Beat Games) in a post on the indie games site Itch.io. “Everything is a little bit rough around the edges, but the core is there and the game is playable.”

Of course, since this is a very early build, there are a few caveats. This is not a full version of “Beat Saber” or a demo, Hyperbolic Magnetism said. It only works on SteamVR and it doesn’t have a user interface menu. Oh, and there might be some bugs.

“Beat Saber’s” concept is simple: the player uses long energy blades reminiscent of “Star Wars” lightsabers to slash at blocks representing musical beats. The game has sold more than one million copies since launch, and it might be the first VR title to do so, Beat Games co-founder and CEO Jaroslav Beck told Variety in March.

Beat Games released the game’s first song pack in March called “Monstercat Music Pack.” The DLC features ten new tracks from the EDM label of the same name. While it’s mostly focused on electronic music, Beat Games said it’s looking to expand the music genres available in-game over time. “We are definitely experimenting with everything,” Beck said.

“Beat Saber” is coming to the Oculus Quest, Facebook’s standalone VR headset. It’s available to pre-order now starting at $399. It begins shipping on May 21.