Do you like the card game Set? This is ProSet. Dots cancel each other out between cards. Create a set of cards by clicking on them. If one card has a purple dot, add a card with a purple dot to the set to cancel that dot out. Add a third card with a purple dot to the set and the purple dot comes back. Create a set where every dot is cancelled out.
The neat thing about this is that to construct the deck, we just make an array of the integers 0 to 63 and write them out in binary. We then use the binary number as an indication that a dot is "on" or "off". Each time we add a card to the selection, we xor the numbers to find out if it's a complete set.
I've been told that if you have a 7 card hand, it's mathematically impossible for there not to be a set. But I often get stuck with just 7, so you get 8.