Context: The IW engine is a game engine developed by Infinity Ward, Treyarch, and Sledgehammer Games for the Call of Duty series. The engine was originally based on id Tech 3 as its core, since the engine itself is proprietary with inclusion of GtkRadiant by id Software. It has been used by Infinity Ward, Treyarch, Raven Software and Sledgehammer Games.\n\nQuestion: what engine does call of duty run on? Let's have some stream of consciousness first.
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The relevant sentence in the passage is: The IW engine is a game engine developed by Infinity Ward, Treyarch, and Sledgehammer Games for the Call of Duty series. So, the answer is The IW engine.
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