@davmac while I see what you mean (yes, I'm going to change that), it does work perfectly how it is in spikes (without the comments). I have tried them all with and without addedToWorld(), however I will try it again since that is logically what will work. You never know, sometimes things just don't work some days :D.

darkmist255, what version of Greenfoot are you using? The code in the Spikes class simply can't work with the current version.

@davmac Version 2.1.2. But what part of spikes won't work? My "getWorld()" in the constructor? I've moved the references to addedToWorld(); Also, I've got it all working. I don't know why, but it just works all of a sudden. Yes, I did put it back into the addedToWorld(), I'm just analyzing the working code right now, then I should be able to avoid this in the future :D. Once again, I was probably tired and just did something stupid hehehe :D...

I interpreted this as "it works as it is posted" - maybe that's not what you meant. I've you've moved the initialization of the variables into addedToWorld() then it makes sense. (yes, it's getWorld() in the constructor that is the problem).