Could've been Great.
But, I found the navigational system to be very clumbsy and at times insufficient, especially when there were more than four enemies on the screen. I think the four arrow keys would have been a better choice, rather than a single key. It wasn't that bad though, the graphics were fantastic and simple and the enemies movements were for the most part, unpredictable. So, it's still a good game, it's just the movement that brought it down.