So this is a frequently used concept in 2002, a side scrolling shooter isn't very original as there are several on the portal very similar to this one. However I will acknowledge the effort you put in on the art.
Noticed a couple bugs right from the start. Enemies spawn on the top of the screen where you cannot go, ships can die multiple times without fading, and you can infinitely hold your shot. Combining the last two you can jack your score up super easily by moving slowly backwards with a ship in front. I ended up getting a few hundred thousand in 30 seconds.