Flip two cards at a time, remember what's where, and clear the board by finding every pair.
All cards start face-down. On each turn you flip two of them: if they match, the pair stays revealed; if not, they flip back and you try again. Recall where you've seen each symbol so you can reunite pairs efficiently. Clear the whole board in as few flips as you can.
Concentration is one of those games that exists everywhere and is credited to nobody, which is what you would expect of something playable with any deck and teachable in a sentence.
Its names multiply accordingly: Memory, Pairs, Matching Pairs, Match Match, Match Up, Pelmanism in Britain, Pexeso in central Europe. None of them is the original, because there is no original to be the version of.
The design is close to irreducible. Every card is face down, a turn reveals exactly two, and the only resource in the game is what you managed to notice when someone else was playing. It is the rare game where watching an opponent's turn is more valuable than taking your own.
Memory is the timeless concentration card-matching game, free to play in your browser with multiple sizes and a daily board. Built in-house at PlayPendium.