Thanks! I really appreciate the feedback and you buying my game :).
I definitely want to add more content to the gameplay to make it more interesting and varied, potentially multiple weapons and also abilities charged up by kills, as well as refine what is already there to feel really good.
I'll definitely iterate on your feedback as well and I have already implemented some of the changes too.
I'm going to check out Super crate box too so that will be cool, cheers.