Check out the guy with his face planted in his keyboard at 9:05!

Is that what spreadsheet debugging looks like?

Edit: at 13:40, maybe he's just using facebook.

Edit2: I'm sorry for putting it that way, I didn't mean to shame him about his vision. I only thought it seemed like he wasn't paying much attention to the lecture when he kept switching between using his phone and laptop, while wearing a "facebook" t-shirt.