Nice little fun MR experience!
There were a couple of issues for me...
Firstly, I'm left handed so it would've been nice to have the option to change the gun hand.
Secondly, I was stood next to a wall when I started the game so the bubble spawner was technically outside the room. So it spawned bubbles outside of the room and I couldn't shot them as the walls would be in the way.
Other than that, a nice, enjoyable MR experience.
It's always a pleasure playing your games Greg :)