Nice work - this is getting better. Maybe next could be to actually display the lives and a score. You may like to have a look at this: http://blogs.kent.ac.uk/mik/2012/02/joc-16/

You would put the WASD commands in all classes that you want to see move in the world (stars, enemy ships, asteroids, ...). The best way to do that would be to make a common superclass for all those classes (say, call it 'ScrollActor') and put the code there, then you don't have to write it three times. If you also have turning, though, then it gets a little more complex, because the new objects enter the screen at different places.

Oops. Linking didn't work. The site is http://www.greenfoot.org/book/

The scenario is part of the Greenfoot book. You can get the source from the [url=http://www.greenfoot.org/book/]book website[/url] . Look for the "Bood scenarions" link.

While you are developing, you can instantiate different levels interactively (by right-clicking your world subclass and selecting "new ..."). The world which you last instantiated interactively will be the one the scenario starts with.