"It's quite simple," she starts explaining, hunting out a packet of picture cards from amongst her heap of cushions. "I shuffle the pack and divide it between the two of us, face down, and then we each take turns placing one face-up in a pile in the middle. If the one you place matches the one directly beneath it, the one who shouts 'Snap!' first is safe and the other has to take all the cards in the middle into their pile. Whoever gets rid of all their cards first wins!"