This is the SCATTER symbol.
All wins are added to the player’s balance after all of the tumbles resulted from a base spin have been played.
Each time a winning symbol explodes, it marks its spot on the grid. After a symbol explodes a second time on the same spot, a multiplier is added to the spot, starting at x2 and doubling each time another symbol explodes on top of it, up to a maximum of x128. The multiplier is applied to all winning combinations that land on top. If more multipliers are involved in the same winning combination, they are added together. In the base game, all marked spots with multipliers are kept until the end of the drop sequence and are cleared when there are no more drops.
Land 3, 4, 5, 6 or 7 SCATTER symbols anywhere on the screen to win 10, 12, 15, 20 or 30 free spins respectively. During the FREE SPINS round, the marked dots and their multipliers remain in place until the end of the round and can increase with subsequent falls throughout the free spins. Land 3, 4, 5, 6 or 7 SCATTER symbols anywhere on the screen during the round to win 10, 12, 15, 20 or 30 additional free spins respectively.