man quite a challenge!
I always have high expectations for bullet games like these.
My biggest complaint is that I would have had at least a 3 second shield after being hit, moments after being hit by a laser I would suddenly be hurt again, this may perhaps be due to keyboard control as its harder to control and is easier to get hit this way, if you could add a mouse control option this may not be of concern. Otherwise a temporary shield so I can recuperate slightly and get away.
I agree with everyone else about getting money, although it wasn't extremely difficult it did take quite a while to get a single upgrade, for this I recommend making it easier to get money then adding many more upgrades, its very thrilling to save up for 3 upgrades that you really needed ever so badly.
The music did get a little boring after a while. But shit its a hard game so I had to find my own music anyway naturally.
All in all I would consider it very worth while. Learn from this so you can make fantastic games!