Since the emergence (mm unit, cm, m, km various) in length more than one group of 2 (A, B) to Quiz format is a game of hit the group with more that the sum (B or A).
When I thought long and total length of the latter group of A, please press the "A> B" button at the bottom left. When I thought long and total length of the latter group of B, please press the "B> A" button at the bottom right.
If the wrong even once the game is over.
Level goes up each time you answer a question, will become increasingly difficult.