Awesome tip! By 'freeware' do you mean something like the Unlicense? http://unlicense.org/ I have to be a bit of a stickler about this, because I'm modelling proper digital citizenship for my kids. :)

Also added if ( dsx == 0 && dsy == 0 ) return; to the beginning of scroll(int dsx, int dsy) so that no work is done if the requested scroll is zero. I love this code. Most compact way of implementing this that I've seen. Very well done! What license is this code under? I have some students interested in using it!

Yes indeed. The change I posted makes the value positive before the mod. They always land on the same value. So instead of: ------------------------------ // find a similar positive value for scroll positions while (imageX < 0) imageX += 100*wide; while (imageY < 0) imageY += 100*high; // get new starting positions for drawing 'scrollImage' imageX = imageX%wide; imageY = imageY%high; ------------------------------ You can have: ------------------------------ // find a similar positive value for scroll positions if (imageX < 0) { imageX %= wide; imageX += wide; } if (imageY < 0) { imageY %= high; imageY += high; } // get new starting positions for drawing 'scrollImage' imageX = imageX%wide; imageY = imageY%high; ------------------------------

Or... given that it looks like you may have added the multiplication by 100 to reduce the number of loops.... if (imageX < 0) { imageX %= wide; imageX += wide; } if (imageY < 0) { imageY %= high; imageY += high; } Should get you there without the loop and without the x100 workaround to try and reduce looping.

In the scroll() method, the following two lines with loops may take a long time to execute if the 'camera' is scrolled very far from world center: while (imageX < 0) imageX += 100*wide; while (imageY < 0) imageY += 100*high; --- Consider updating this to if (imageX < 0) { imageX %= 100*wide; imageX += 100*wide; } if (imageY < 0) { imageY %= 100*high; imageY += 100*high; } -------------------- This replaces a looped add with a single mod and a single add.

@AreebRaza: There are some loops in the createTextur() method of the ScrollingWorld class that might take a long time to complete when the player is very far afield. Here's a version without the loops that uses mod math to do the same job. /** * Creates a moving textur on the background image of the world. */ protected final void createTextur() { // Higher performance version: int x = totalXMovement; x %= textur.getWidth(); if ( x > 0 ) x -= textur.getWidth(); int y = totalYMovement; y %= textur.getHeight(); if ( y > 0 ) y -= textur.getHeight(); getBackground().clear(); for (int i = x; i < getWidth(); i += textur.getWidth()) { for (int j = y; j < getHeight(); j += textur.getHeight()) { getBackground().drawImage(textur, i, j); } } }

I like it! It'd be more difficult if the player could die even when moving. To keep that from making it too difficult, you'd want to add the ability to face/move all 8 directions, and have the World only add new zombies at a certain minimum distance from the player.

Forgot to evaluate a finished game extra high/low. This helps the alpha-beta algorithm cut off more of the search tree and move faster.

This is some really great work! I've been working on extending this as a base for a real-time strategy game a student of mine wants to create. I seem to be having problem with collision detections utilizing getObjectsAt(int x, int y). It seems like that method has some weirdness when called off screen.