Multiple Expanding Symbols is an enhanced version of the 'Special Expanding Symbol' feature, a powerful system where, primarily during a free spins bonus, two or more types of regular symbols can simultaneously gain the 'Special Expanding Symbol' ability through retriggers.
The core of this feature is to go beyond the limitation of the original method where only one symbol expanded, providing immense potential for multiple types of symbols to cover the screen simultaneously as the round progresses.