Awesome game
First of all, I am a big fan of shooter games. What you've made here is easily on par with titles like Raiden or the 19xx series.
The graphics were nice, the game was definitely very colorful. I liked several of the effects that you used - particularly the 'transition' into the second level - good work on the cloud effects there. And, of course, MaestroRage's skills in the audio department are always a treat to listen to. I definitely enjoyed the lack of any other sounds in the game - nothing to distract from the rest of the game.
Finally, all around it's enjoyable. Not too difficult, and you get more than a fair share of lives to last you through the five minutes. The medals are tricky to get, but that the point, isn't it? This game makes you work for them for a change.
Great game all around. 5/5, 10/10. Keep up the excellent work.