Totally has potential...but....
Well, like you said in the description, the game has a lot of potential. However, when you're on level 3 and the enemies are coming WAAAAY faster than you are even close to capable of shooting, (let alone on both sides), people tend to get mad.
The upgrade system could also use a bit of work. Mind you, I found out that you could repeat levels, which is very helpful in one's quest for the ungodly amount of money needed, but needing to replay levels 1 and 2 seven-hundred times is kind of a buzz kill.
One last thing that I need to say: The gameplay is painfully slow. This can be solved with a couple extra weapons...and, just perhaps, a character that can either walk, (or at least roll), from the beginning. A hopping head has it's fun-and-games quality...but Jesus can it piss off a gamer.
Overall, it needs some work, but it's got great possibilities of becoming a far, far better game. Keep working, dude.