If not a scoring system, how about a progress bar (showing number complete vs. yet to go)?
Also split pairs from each other in progress order (e.g. up-down followed immediately by down-up).
Also split pairs from each other in progress order (e.g. up-down followed immediately by down-up).
Progress bar would definately be useful even if subtle.
The pairing is not a bad idea, let me give that one some thought