I have been enjoying the Introduction in Josh Waitzkin's Academy. I made it to page 75 of 82 in the Mastery Quiz and it seems that I am tasked with using a king and queen to checkmate a lone king. Unfortunately I am unable to select and move the white pieces. When I hit next for page 76 I am greeted with "Congratulations!" even though I didn't get to do anything. Is this a bug with page 75 or am I just misreading the card?