How about triangles and making the stroke/fill transparent?

dipika

I think those are two vital components that should be looked in to adding to the Hour of Code!

shiffman

Thanks for the feedback. In order to keep the tutorial simple enough to take place over an hour, we decided to leave a lot of additional details out. It's our hope that we'll be able to lead folks to more involved tutorials that cover these ideas.

If you are looking for these functions, take a peek at:

http://processing.org/reference/triangle_.html

http://processing.org/tutorials/color/

GoToLoop

At least you should teach folks how to declare their own variables, rather than just using mouseX/Y & width & height! :P