Pretty Good
This is a pretty good game considering that its your first. If I might have a suggestion perhaps using keys on the keyboard like the Arrow Keys or W,A,S,D for movement and perhaps Ctrl, Enter or Spacebar for shooting. This would probably make the game more enjoyable because when using the mouse it can get a little hectic if you have been playing for a while and if you bump the mouse or if something else happens that makes the player uncontrolablly move the mouse (eg. Sneeze, Get frightened by something) this can cause the ship to hit an enemy causin the player to lose a life.
All in all this is a fairly enjoyable game and considering it's your first you have done a very good job.