Find the Match — two players, one PIN

Two players, one device, and the strangest little puzzle on the site. You each get a circle of eight objects, and between any two circles there is always exactly one object in common — never none, never two. Spot it and tap it before the other person does. It works because of a piece of geometry rather than luck, which is why the shared object is often the one you have already looked straight past: the size and angle change between the circles, so your eye keeps sliding off it. First to ten points wins.