When you export from Greenfoot, the export dialog has a checkbox named "Lock scenario". By default it is checked, but if you uncheck it, you can change the speed of the game on the gallery.

It got a lot more difficult now. Especially in the beginning it depends a lot on how lucky you are with the enemies approach. To hassan: you use the mouse to buy upgrades, but I guess you now that since you got to level 2. The trick is to figure out which upgrades to buy at which time. Davmac wrote a bit about that in his post.

Nice game! And it even teaches you something useful. You should consider submitting this scenario to CodePoint by adding the appropriate tag.

When we did the Greenfoot competition at JavaOne (last year?) someone actually created a nice game based on this. The goal of the game was to herd sheep into an enclosure by using the mouse to move a big red button that the sheep apparently didn't like. Unfortunately I think we might have lost that scenario because it was created with the very first version of Gallery (when it was still called MyGame)

I survive about 1ms if I don't change the speed... Level two should have more planets! And maybe something that repels the snake.