Simplest possible IR bumper

I have written a brief tutorial about simple but yet effective IR bumer sensor. It can be used for novice-level obstacle avoidance, if Sharp rangefinder is not available, or in the situation when additional info is required. However, it will not work properly as distance sensor because different materials reflect different part of incident light, and black body will be seen closer than white. However, it works very well to guide robot not to ram walls :) I compiled my tutorial into PDF file. I believe, it looks well. Code example may looks complicated, but I am not a pro(grammer) really, I think main idea will be clear.