I am very sorry about how late this reply is. I suggest you restart your computer and try again. I can't really help you to much in the area of java heap space errors, most of the time the code just won't work on that particular computer.

You can make the world as big as you want. Where the code says GreenfootImage back = new GreenfootImage("Cave.png"); Just replace Cave.png to whatever the name of your file is.

Hey , this is really cool, and I know you are real good with physics and math so do you think you could figure out a way to have the character angle with the slope of the current ground beneath it, because I am thinking about making a dirt bike game, and I want it to have really nice physics so maybe you could help me out. I would need to calculate the mass with velocity in addition incline and the weight pulling down a slope, and making it jump into the air, keeping a proper path, and maybe like ragdoll type physics with bike tires and the rider. It is a huge challenge but I would like to attempt something like this.

@jrlowe, I am very sorry about how late I am getting back to you on this, but yes, I believe it wouldn't be to hard to make the rider rotate with the ground. I have though about creating a game similar to what you are considering. The hard thing about what you're mentioning would be the rag-doll physics - that would be very difficult. Perhaps I will implement the idea of rotating the actor to the ground in my scenario.