a smaller size pen highlights errors in the system

I need to find the 2.5 mm round point markers again. I got them at Dollar Tree but they haven't had them the last few times I was there.

undrawing

I was tinkering with the size that I draw this picture so I didn't bother to erase the board before I drew. It turns out the pen had just died and it undrew. Looks kind of neat. I may have to try this on purpose with some of my old markers.