If you want others to be able to have access, you must check the 'Publish source code' checkbox every time you upload/update the scenario.

If and when you manually add actors into your world, please 'Save the world' before uploading the scenario. All I see above is sand, which is not 'cool'.

Or you could download my Image Transparency Addeer/Remover scenario. Just run, load and save. It will automatically reduce it to minimum image size. It is located here: http://www.greenfoot.org/scenarios/7423

I think you are required to key a number in for the other color parts (at least zeroes, if that is the value you want for them). You could programmatically account for an empty return string. I do not know if setting a default '0' value for the inputs would be enough.

In fact, with a little testing, I figured out that the current act cycle completes before the scenario is actually stopped (in other words, even if the 'stop' was in the world class act method, all the actors will still have their act methods run afterwards before the scenario stops).

You missed fixing this one: * greenfoot : move left/remove at edge should check '<= 0' Also, somewhere you stated that the statement after a 'Greenfoot.stop();' statement would not execute. That is not true. The method will still finish even after the 'stop' statement (and the current 'act' method will also finish up, even if it calls a method with a 'stop' statement in it).