Pebbling a Chessboard

Got a bit carried away with this video about pebbling a chessboard.

The video features Zvezdelina Stankova and was filmed at MSRI.

Here is part one:



And here is part two (part one is required viewing):



Here is a roughly-edited part three for people who are really keen:



And here is a section I cut from part one about the "invariant" - I thought people might it find interesting and it makes part one easier to understand…. but it also makes part one very long, so I chopped it!!!