Simplify the following text for a Grade 8 native English-speaking person.
Original: In Mario Kart Wii , the developers were able to incorporate motorbikes . The game was called `` Mario Kart X '' internally for a while , before deciding on `` Mario Kart Wii '' .
Simplified: Mario Kart Wii is a kart racing video game made by Nintendo for the Wii game console .