I will echo what people said. It’s a really addicting game. Very solid and hard to criticize for me. If I really had to try, I’d say it lacks a bit of a goal. At the beginning I felt like shooting things down and becoming stronger, but that feeling stops after a while, which is normal, but there needs to be a reason to continue playing and pushing through it. Maybe give it a max amount of time you have to survive or something? Anyway, that’s just my opinion though, I’m sure you also have a bunch of ideas of how to take this even further.