and (6) you are updating the image of your counter every act as well. It will only need updated when the score actually changes (only when a projectile hits an enemy object).

A few of things that could be improved on: (1) you are calling 'MusicLoop' unnecessarily from the act method of the 'GameOverMusic' class and the 'AlienSpawner' class. It would be better to have them in their respective world classes as 'static final GreenfootSound' fields; and that you use the 'playLoop' method on them (so you do not need to check on the status of the sound every act -- they will loop automatically). (2) all the code in the 'AlienSpawner' class should go in your 'testWorld' class. Adding an extra actor object into the world is not needed to perform those actions. They can be done in your 'textWorld' class act method and the 'AlienSpawner' class can therefore be eliminated. (3) a Projectile object is NOT a Rocket object and therefore should not be subclassed as such. (4) you could probably simplify the code in the Projectile class by just looking for an 'Enemy' object and use the 'instanceof' keyword to determine which type was found (if any). (5) there is no need for your timer to show that precise a value. By only updating every, say, tenth of a second, you will save oodles on CPU usage.

There is an awful lot of lag for what this scenario does. Are the asteroids the pass the left edge being removed from the world? How about the bullets that pass the right edge? Are you sounds saved staticly or recreated each time they are used? Can you re-upload with source code to acquire help along these lines?

@dan11, how would you go about fine tuning the game in this situation? (not that I need to know, myself -- but for others, and for K_wow). To clarify: when simplified by moving one pixel at a time, you can move left, right, up, or down, at a speed of one pixel per move; but, when moving diagonally, you cannot. Then, you must move by multiples of the square root of 2. That is the distance between two diagonally adjacent pixels.

@vakz2013, play the game while logged in. At the end,, the high scores will show with button across the bottom of the window to view the different classes or start a new game.