I agree that the graphics are really the power of this game. It fits the style perfectly, and the use of the 3D box is great!
I'm afraid i didn't like the gameplay at all, probably because i kept dying and i felt like i could do nothing about it.
I had a really hard time dealing with the combination of a tiny player the same color as the enemy bullets, and super fast speed and acceleration. And i lost track of my ship all the time. Because of the sensible controlls i couldn't dodge a bullet without having a 50% chance of hitting another one. The precision movement was better then nothing, but i would prefer a mouse controlled ship.
Maybe you want the controlls to stay as they are in order to keep the same type of gameplay, but i think you should do some changes to the players spaceship. Not nescessarily redesign it, but change the color or something. Right now you can't focus on the enemies you're shooting at without your ship getting lost in the storm of bullets.