US Patent 7918726 Slot machine and playing method thereof

When the number of bets is determined and a game is started, reels start spinning. After a lapse of a predetermined time, fifteen symbols are repositioned in symbol display regions. Particularly, in case a “RED7” symbol or a “BLUE7” symbol is included in the repositioned symbols, an animation effect to represent a volcanic eruption of a volcano, a performance character, and a sound effect corresponding to a volcanic eruption sound of the volcano are outputted by dragging and dropping the “RED7” symbol or “BLUE7” symbol to a crater of the volcano.