You each get 20 cards: 5 in your hand and 15 in your deck.
Click a card (or press 1–5) to put it on a centre pile. It fits if it's one higher or one lower than the top card. Suit doesn't matter, and A and K wrap.
Your hand refills from your deck after every play. You both play at the same time, so be quick!
If neither of you can play, the side stacks flip new cards onto the piles.
The first player to empty their hand and deck wins.