I got the idea when looking at some sunset pictures on freefoto.com (where I got all the background photos from). Just a couple simple keys to do things with this. You can press 'A' to clear any drawing; press 'SPACE' to redraw (keep pressing to get a whole flock!); and LEFT and RIGHT ARROWS to switch through the backgrounds. Clicking the green flag, will clear the last drawing and do another one. I like doing that until I get a picture I think looks good. (advanced example of a mixed media project. This project incorporates images from online sources as background and adds dynamic drawing with sprites over the images)
