That magic takes advantage of people's habitual thinking that the total number of coins on each side has not changed, but in fact the total number of coins is still increasing.

After adding a coin to a pile of any "side group", there is only one more coin on one side. Just move the one on the corner to the "side group" on the other side to ensure that the number of coins on both sides remains the same, and the total number increases by one. The same is true of "Angle group".

This should be a book from Liu Qian, right?