Some comments added here and there.

Note that when we copy/paste at the end of lecture from the iPad storyboard back to the iPhone storyboard we CAN copy/paste the URL-showing scene too if we want, even though it is in a popover. When we do so, the segue will go from being a Popover segue to being "Unknown" (because there is no Popover on a phone, only on the iPad). No problem, just inspect that segue and change it from Unknown to Push (this has been done in the posted code below). It will all just work! Possibly this is not the best UI for showing the URL on a phone, but it is serviceable.