While this game is admittedly a bit simple, there is nothing more addictive to me than trying to beat my own score. Although the game maybe started to get a bit repetitive after a while (I think that enemies started to speed up a bit, which helped a little), watching that little number go up was pretty effective in keeping me going, haha.
I was a bit confused as to how exactly the color changing mechanic worked. It seemed that maybe I was able to shoot enemies when they were one color, but not the other? I didn't totally understand it, and it unfortunately seemed to have very little effect on the actual gameplay.
But besides that, this is just good, simple fun. Isn't anything wrong with that!