[photon]

I've seen a few different ones like that, really cool.

Makes sense too, falling over like dominos makes sense, and they're spaced such that if they're slightly tilted the top edge holds up the previous tile on top. The final tile has no such tile to rest against to it falls flat, meaning the previous tile has nothing to rest against so it falls flat.. removing the ledge the previous tile was sitting on so it falls flat, etc etc.