Enjoyable and very well presented game
I really enjoyed this, it reminded me of the good old days of Smash TV and Gauntlet on the old arcade machines when I was younger.
It plays really well and the smoothness of the control system does really help, especially when you get to the later levels. The thing that kept me playing was the implementation of the weapons shop and upgrades system which, much like your other game Sentinels of Mijil, give a good feeling of continuous achievement as you strive to get that next upgrade (I get the feeling that Dead Space may have figured as a source of inspiration?).
In any case, the only real fault that I see within the game are the repetitive environments and rather drab level design, but given the Shoot-em-up arcade machine feel of the game as a whole, this doesn't really affect the overall enjoyment of the game.
Right, quick conclusion then:-
Good Points - Gameplay, Concept, Implementation and making me feel like a kid in an arcade again.
Bad Points - Drab Level Design, Repetitive..er..ness and, while I think about it, no big bosses.
Score - 8/10