Gem Block Destruction & Fill is a highly dynamic reel modifier that operates in two distinct phases. Upon landing, special 'Gem Block' symbols (e.g., Red, Blue, Green) trigger the first phase: the complete removal of all regular symbols on the grid that match their designated color-class. The second, crucial phase then immediately follows: during the subsequent cascade, only symbols of the *same type* as the destroyed color-class will drop into the empty positions. This creates a powerful and often high-paying board state where the grid is filled entirely with one type of symbol.