Specifically, it looks like upcoming turn-based RPG Mario and Luigi: Brothership was developed using Unreal Engine.
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Very rarely do we see a Nintendo title not being developed using the company’s proprietary and internal development toolsets, but that has certainly been not quite as rare of a sight in recent years as it used to be, with another upcoming first-party title seemingly confirmed to be developed using an external engine.
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This would make Mario and Luigi: Brothership the fourth Nintendo title to have been developed on Epic Games’ engine, following in the footsteps of Princess Peach: Showtime!
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Mario and Luigi: Brothership is due out on November 7 for Nintendo Switch.