I think the concept is amazing! I had a fun time running around the beautiful atmosphere. The movement of the main character was very fluid. I could just sit back and watch the worms go in and out of the ground shooting their particles all day. It was kind of relaxing.
The gun took a bit of time for me to control but I got the hang of it. The menu system looks great.
I think you created a new genre "RTPS" relaxing third-person shooter.