The games have used different battle systems. Before "Final Fantasy XI", battles were turn-based. The main characters and bad characters were on different sides of the battlefield. "Final Fantasy IV" introduced the "Active Time Battle" (ATB) system. It made better the turn-based system with a time-keeping system. This system was designed by Hiroyuki Ito. It gave a feeling of urgency and excitement to the fights. It required the player to act before an enemy attacks. It was used until "Final Fantasy X". This game had the "Conditional Turn-Based" (CTB) system. This new system returned to the old turn-based system.