Flip the cards, remember what's underneath, and clear the board by finding every pair.
Tap any two cards to flip them over. If the symbols match, they stay face-up. If they don't, they flip back and it's the next attempt. Clear the whole board by matching every pair — try to do it in as few moves as possible.
Easy uses a smaller 3x4 grid for quick rounds, Medium is the standard 4x4 grid, and Hard steps up to a 4x6 grid for a real memory challenge. Your best move count is tracked separately for each difficulty.