Your goal is to beat your opponent by scoring more points. You score points by melding cards, and making as many canasta as possible. A canasta is a meld of at least seven cards of the same rank.
Each player starts with 15 cards in hand. Yours are visible at the bottom of the window.
Both players take turns in drawing one card from the stock, and discarding one card on the discard pile (in that order). Both players take turns in drawing the first card.
After drawing a card, a player may meld cards if (s)he wants to. Cards are melded in columns of at least three cards;
e.g. you can meld three Kings, or four Fives. You cannot meld sequences like Four-Five-Six. Once a card has been melded, it cannot be taken back into the hand (except with the Undo meld option).
When a player has melded his cards, he ends his turn by discarding a card. At that point, his melded cards are checked to see if they conform to the canasta rules. Discarding a card is not necessary if the player can go out by melding all of his cards.
Instead of drawing a card from the stock, a player may take the entire discard pile. However, this is only allowed if he can directly meld the top card.