Kind of your generic shooting game.
~ Animation/Graphics ~
Not too bad at all. Very basic, simple, generic, etc.. Looks just like the old arcade style games that I would play when I was a little kid. It made my computer laggy, but that's because of my slow dial up internet. :P
The game was actually kind of easier during a lag.
~ Story/Content ~
Like I said before your generic space shooting game. I think there is only one thing that you could do to make the game better. I would add upgrades to it if at all possible.
With a game like this you could have upgrades fall from an enemy. You could have different types of guns, shields, spped, etc.. Even some that made things worse like making your gun slower, taking your protective things away, etc..
If you didn't want to have upgrades in the level like that you could have some in a store type of set up in between levels. They could get a certain amount of money for how fast they beat a level, how many times they died, perhaps have money fall from the enemies, etc.. Or they could just have a set amount after each level and they have to choose carefully.
In the store you could have upgrades such as faster gun, bigger gun, temp. shields, more strength so you have to get shot more than once to die, extra lives, etc..
That's just an idea though. That's completely up to you. I personally think it would make it more fun.
Also, add a pause button please. :(
~ Audio ~
The sound effects were great! Perhaps a little bit of ambient space type of music in the background could make it a bit better, but I didn't mind it without the music.
~ Overall ~
I hope you like some of my suggestions and if not, still a decent game all around.