Hello,
It's good and fun to play. Just love the controls and the camera movement along, well done to keep it minimal and well polished, the map too in the left corner suits the theme well. How about changing the unlimited amount of ammo to something limited and the player would get the ammo when he kills one enemy, just an idea to me the resources useful. Also, how about adding a small camera shake while the enemy gets destroyed and introducing some follow target missiles that tend to available after a few kills or some cool powerups. Lastly, breaking the game into smaller sections and environments would give a nice feel of progression to the player.