very good - toilet paper tube is exactly what I was using here while looking at our (worn) kitchen table. I already mentioned it in a comment further below, but just to make sure you can read it as well: It's a game I play with my kids to show them how easily our eyes can be tricked - or rather the brain/thinking which connects the "schooled" in-formation to the picture the eyes transmit... :-) you can even move the papertube over the table - try it out! Cheers from the Seven Mountains in Germany