Stack is a competitive game of timing in which players compete to knock more blocks from the "Stack" than their opponent. To acheive this, all that must be done is hold the fire key down ('A' for player 1 or 'L' for player 2) to charge their cannon, and release to fire at an active block. This process is repeated until a player has reached the preset score. If you dont understand these rules, setup a quick game and try it out for yourself, you'll soon find how easy it is to get the hang of it...