US Patent 8105145 Gaming machine having positional expanding symbols

A gaming machine for conducting a wagering game includes a value input device for receiving a wager and a display for displaying a plurality of symbols arranged in an array of symbol positions. The plurality of symbols include at least one expandable symbol. The plurality of symbol positions include at least one expandable position. The controller is operative to vary the symbols displayed in the symbol positions, and if the expandable symbol appears in the expandable position, expand the expandable symbol into at least one other symbol position to form and display an expanded symbol.