While the first three Mass Effect games were all made with versions of Unreal Engine 3, BioWare began using EA's in-house Frostbite engine for all its games after that. The transition wasn't easy—the first two Dragon Age games had been made with versions of the studio's own Eclipse Engine, and according to Mike Laidlaw that change was why Dragon Age 2's expansion Exalted March had to be cancelled.
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