Six drawings on the left, six labels on the right, and two minutes for five trays. Tap a drawing, tap the label that belongs to it, and the reason prints underneath. A wrong pair costs you four seconds.
Scoring. Every pair is worth 300 points. Three pairs in a row with no miss lifts the multiplier, up to three times. Clear a whole tray and you get 500 points and ten seconds back.
The cost of a miss. Nothing is deducted from your score. Four seconds come off the clock instead, so the clock itself is the penalty.
The drawings. Every bone, part, gland and vessel on screen is drawn in the page itself. Look at the shape, the landmarks and where it sits, not at the colors.
At the end. Every pair you missed on the first try is listed again with the reason, so the list is the part worth reading.