Didn't really know what to expect, but this was honestly kind of awesome.
The shielded enemy was a great use of the mechanics which i enjoyed a lot.
The last level was really good too - starting with the clever puzzle of the floor being scale-able, and ending with a real novel scenario of having to create an arena as you're fighting. Would love to play an arena shooter that's nothing but that, to be honest.
My only major criticism is that the gun-building didn't really do much for the game. Increasing and decreasing size are just opposites of eachother, so there isn't really any interesting way to combine them. The ending hints at some more interesting options like scaling yourself, but as it is, it'd probably be perfectly fine just using a slider, or even just reducing it to a binary shrink/grow option.
The lack of a proper crossheir for the shielded enemy was kind of annoying too.
But there's a lot of potential here.