It's a reasonably good game, pretty challenging.
Although that one-hit instant kill quite annoys me. The enemies are fast, and even though you have a vague idea of what exactly killed you, you don't know for certain because the game immediately transitions to a Game Over screen – which you can't confirm to start a new game (!).
I'd show your ship exploding, just so you have a few more moments to notice what happened.
I don't know what's the point of even having levels when you can't restart a level and always start the game from the beginning. I don't know how long the game is, but what about three lives or restarting the game at the beginning of a level?
Also, for first time players, parts of the background might look like enemy missiles (especially the largest red star at the right).
Don't get me wrong; it's a good game… just being stuck with Game Over screen after the very first mistake may be frustrating.
Welcome to Newgrounds, by the way!