Easy . Refund the cost of all the upgrades , give them back the amount of cards it took to get it to the level , and bring it back to level 1 . Then divide that number by 10 to the nearest whole number . Then they can upgrade it back to where it would be , but since rares take more cards for upgrades than commons , a level 12 RG might only be a level 9 or 8 rare . <| sep |> the FBI system <| sep |> Can confirm . I was driving my car down a hill , music blaring when the engine stalled automatic transmission and I didn ' t notice because of the loud music . Only when I got to a corner I noticed it was difficult to steer but I put a lot of force into it and pressed the brakes which had a lot of resistance and pulled over to the side . Then I noticed that my engine had stalled . It ' s a 2003 Japanese car though so it ' s still mostly mechanical .