The classic issue with gaming is how to make a level. How to do that in processing? One way is to use images as base for levels. Important here is to use png's and not a lossy format (e.g. jpg). The idea here is to make a small image (light in bytes) that can be used as a "map editor", then processing checks each pixel and draws a square corresponding to the image, but with a rectangle that can be used as a boundary in the game.