Much potential, little delivery.
This game is okay, but it could be so much better. The pulsing background, as has been said, hinders gameplay, as do the movement controls.
Holding down your left mouse fires slower than hitting it repeatedly, much slower. Therefore, it takes some skill out of gameplay and puts it into who can hit their mouse button fast enough for the longest time. But that doesn't even really matter because it's impossible to die in this. I'm fairly certain the blue power-ups are putting my "memory" at over 100. Because when I decided to stop I had to sit there for about thirty seconds purposely getting hit by the things before my memory started going down on the HUD. I wasn't even sure what the red power-ups did, but I assumed it had something to do with my attack.
My suggestion would be to make the amount of memory gained from the blue power-ups less, cap the memory at 100 and give points for getting blue power-ups while at full health. Red power ups increase attack speed, give additional attack tiers (2 parallel columns of fire instead of one, waving shots, exploding shots, etc.) and work on the gameplay over the graphics. Graphics always come second to gameplay. This is a well made game and you should make it perfect!