Is it too flat?

I don’t how to tell if my game is enough, but anything I make make me keep playing my own simple game.

I am trying this shoot em up prototype, where the player shoots meteors falling from above. Destroying adds to score which lets player add more guns using space bar which deducts the score.

Wish I could have uploaded an applet but here’s a JAR to my prototype. I would appreciate your advices and feedback. Thanks.