@Singunner, go to your control panel and click on the java icon (it might say 'Java (32-bit)'). Then go to the miscellaneous tab and make sure the Exceptions Site list includes the following entry: http://www.greenfoot.org/

@Singunner, I am sure that your issue is not unique to this scenario. You are most probably getting the same message on all scenarios you try to access. There may also be a java setting that needs to be tweaked (java control panel).

In the Mover class, in methods 'canMoveRight' and others, where you get a list of each type of barrier, you do not need to ask if the list is null as there will always be a list returned -- it might be an empty list, but it is a list just the same. I will not ask, but suggest that you just set 'vSpeed' to zero in the 'onGround' method of the Mover class. Then you will not need to ask the programmer to add the code at the end of the act method.

Add a line before calling 'segende' in the act method of the ND class to exit the method if the actor is not in the world: if (getWorld() == null) return;

@Doggygaming, I looked at your uploaded scenarios and I did not see any major problems with them. You seem to have much of the basics down pretty good. You must realize that I have many years of practice behind me.

@Doggygaming, you could try a different browser; or, there might be a setting in the current one you can change to allow applets to run in it.