Very cool, but there is a bug with the tree generation. The programm doesn't stop generating trees. When you hit stop you can drag a huge amount of tree-blocks away.

@actinium Yes I thought about the max number of steps in a level. I can't find the crash you mentioned. In which cell you have to go, that the game crashes?? @Entity1037 Why is it better using a, s, d, w instead the arrow keys??