A few little flaws
Overall, the game was quite fun and well done. There were, however, a few flaws.
First, the movement was floaty and a little loose. An unfortuante effect was overcorrection on my part, which would sometimes result in my mouse leaving the box a tad. When this happens, the ship automatically moves toward the upper right corner. It would have been nice if the game paused when you moved your mouse too far, as a few games on Newgrounds do.
In addition, after getting max speed, the ship seemed to bug out. I would move in a direction and my ship would stay in place, then zoom across the screen. In addition, the last boss had a little lag. This issue only increased after defeating him, making a longterm continuation impossible.
Great idea, very fun, needs a little work here and there.