This is a very nice looking game.  The controls felt awkward until I realized WASD moved the tank as well, then that was good too.

The lack of sounds isn't too bad, but there should definitely be some kind of background to fill all the silent portions of the games.  The effects you do have are good though.

The gameplay is pretty good but I agree with other comments that there's a lot of backtracking and just getting through boxes, which feels more tedious than challenging.  

I really liked the level loading effect, but I think gameplay and communication of what's happening to the player was lacking. The merging effect would have been nice if you effectively had some different weapon parts or features that'd merge instead of only with numbers.

Pathfinding would have been nice, but moving with WASD might have been even nicer. I liked the bouncy move a lot :D

In any regard, it feels like you worked on what you wanted to work on, and I think with small changes this could be a much nicer experience!

Couldn't really find how it was related to the theme though I liked the Graphics.
Also just being able to click and move to the tiles right next to you is annoying.
Not to mention the fact that Range 2 Weapons can't hit stuff on Range 1. 
Also couldn't figure out how to reload~