Okay, that is really cool. I was half expecting something rediculous like the quadcopter "flying printer" stunt. These bots actually seem to make a fairly sturdy and precice structure. Also, it seems to go further vertically than previous large structure printers, tall enough to actually print-in-place practical structures.

That said, I don't want to rain on their parade... But how would they make a door in their structure? Or close the top?