I think there should be a way to earn silver, gold and mythical boxes in credits for example 50,000 credits for silver, 100 or 150,000 for gold and 200,000 or 250,000 for mythical, and i think you should make a 0.5% chance of getting a mythical in an item box that means every 200 or so item boxes. I also think you shouldn't be able to use a mythical until level 30 just so you cant get a needle blaster out of a silver box from campaign at level 3 and ruin lower rank ladder battles for newer players. Thanks!

yes is very good idea!