Progress meters have become a common alternative to the sudden scatter trigger. Certain symbols are collected across ordinary spins, a bar fills gradually, and the feature begins only when the bar is complete, which spreads the anticipation over dozens of spins rather than concentrating it in one. In unlock free spins slots of this type, the round is earned incrementally, and the purchase button, where present, simply fills the bar instantly for a price. The meter usually resets to empty once the feature ends.