How the drill works
Choose a line and press Start. The other side's moves are played for you; on your turn, play the book move. A wrong move lights up the right square. If you play a move from a different named line, you are told so (it does not count as a mistake).
A run with no mistakes brings the line back after 1, 3, 7, 14 and then 30 days. A line with a mistake comes back tomorrow. “Review today” drills every line that is due.