Fans discovered an unfinished tower defense Zombies mode in the PlayStation 4 version of Call of Duty: Black Ops 1, more than 15 years after the game’s original release, according to IGN. JTAG, a YouTuber, identified the mode during testing of the recent PS4 port, posted gameplay footage, and said the unfinished mode allowed players to place turrets in a maze‑like map and engage enemies on foot. The footage showed a tower defense element where turrets could be positioned to block zombie waves and players could also shoot enemies directly from the ground. The mode has appeared in later Black Ops titles, according to the IGN article. Treyarch has a history of testing unconventional Zombies concepts, and the secret mode reflects the studio’s practice of exploring alternative gameplay ideas before finalizing content, as reported by IGN. It is unclear whether the mode will be revived in future titles.