The E3 demo of Mario Kart 7 has been preserved! It shows Mario and Luigi racing on early versions of Mario Circuit, Alpine Pass, and Wuhu island!
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Wuhu Island is the most unfinished, as the only finished parts are from the Red Gate Bridge to the ruins. There is also a different version that was probably a model import fail from Wii Sports Resort, as many parts are improperly textured or just missing entirely.