Now that was a really fun gun! I got tripped up on the level with the 3? pits but I eventually got it. I thought it was kinda funny when the balls would be on top they just sorta bounced around, added a little bit more of a challenge. Gameplay loop is nice and straight forward.
There is one thing I want to mention, we had this problem last year, on Unreal make sure you disable the SteamVR plugin as it can cause issues with some people when starting games. That's a pretty minor thing though and I've only ever seen a handful have issues!
Overall great job!