Love the moment of him smiling, terribly amused by his own dry explanation and the demonstration, probably in contrast to the bored students. Just for the sake of nitpicking for improvement, “in onstage” sounds odd, and I think the “in” is unnecessary. Also, in science lingo, one wouldn’t say 100 squared. The usual way would be to say 10^4.
Pyropunk 51 (PPP LoA) 
THX 0477