I'm not exactly sure what problem you are having.
At the moment your program ends as soon as you have shot the last invader because of the check in the 'gameover' function. If you comment out line 142 (I notice you are using protean) then you will see the animation play as you shoot the last one.
At the moment your program ends as soon as you have shot the last invader because of the check in the 'gameover' function. If you comment out line 142 (I notice you are using protean) then you will see the animation play as you shoot the last one.