For added fun and excitement, old single-point resistive touch displays have a quirk even stranger than only registering the last touch if they were touched in more places than one. In all of them I’ve messed with over the years ranging from industrial control panel monitors to PDAs to the Nintendo DS, they actually register the touch at the average coordinates of all the places on the screen where the touches are. I.e. pretty much exactly in the geometric center of all of the points. If you still have your old DS lying around you can try this for yourself.