Active Time Battle (also abbreviated as ATB) is a role-playing video game mechanic invented by Hiroyuki Ito. It was first used in the 1991 Final Fantasy IV, and patented in 1995 by Ito and Hironobu Sakaguchi, though the patent expired in 2010, allowing it to be used in any game.[1] It added a timer bar to turn-based gameplay, allowing both protagonists and enemies to attack at their own pace, even while navigating menus. Different types of techniques caused the timer to move at different rates until the character could move again. The system's success led to it being used in most subsequent mainline turn-based Final Fantasy games, up until the series eventually abandoned turn-based gameplay in favor of action role-playing gameplay for mainline titles.[2] Active Time Battle has been noted by critics as a revolutionary step in the genre as well as a defining aspect of the series' Super Nintendo and PlayStation era games and of Final Fantasy as a whole.