Block Solitaire is a two deck solitaire card game where the player builds up 8 foundations by suit from Ace to King. The 12 piles can be built down, and the player may only move the top card in each pile. When the player gets stuck, another 12 cards can be dealt from the deck onto the 12 piles by clicking the game deck at the bottom of the game screen. Whenever a pile has all the cards removed from it, the empty space must be filled by a card from the stock pile, as long as there are still cards in the stock pile. The player wins when all 8 foundations have been built up from Ace to King.
In Block Solitaire and Flip Block Solitaire, the piles can be built down without regard to suit. In Pro Block Solitaire the piles must be built down by suit. In Flip Block Solitaire, half the foundations must be built down from King to Ace while the other half must be built up from Ace to King.