In most memory games, the board is dealt again every round. In Odd One In, it stays. That is what makes each round a real test of memory.
The board grows, then fills up
Round 1 shows one object: tap it to start. Each round then adds exactly one new object. While there is room, it lands in an empty place. Once the board is full, it replaces an old object instead, so its position gives nothing away. The board keeps getting a little bigger during the whole game.
An object that leaves never comes back
An object pushed off the board is gone for good. You never have to wonder whether an object is new or was seen fifteen rounds ago.
Look-alikes and shuffled rounds
From round 7, the new object is sometimes a look-alike of one already on the board. From round 10, some rounds shuffle every position: the screen says Shuffled!, and only the objects themselves can guide you.