Simplify the following text for a Grade 6 native English-speaking person.
Original: In North America , GameStop and Rockstar collaborated on a pre-order bonus in which customers could vote for one of three outfits that Marston could unlock in the game .
Simplified: In North America , GameStop and Rockstar worked with each other on a pre-order bonus . This bonus would let customers vote for one of three outfits that Marston could unlock in the game .