The keyboard shortcut "Opt-P" for going to the next lesson is not working for me on the Mac in Chrome. Instead it inserts the text " , " and highlight it. Here is a screencast of what happens when I hit Opt-P three times.
I have tried it in incognito and get the same thing. Cmd-Enter, Opt-N, and Opt-R all work fine. It's just Opt-O that isn't working.