The First Try Challenge is a repeating event that lasts 48 hours. Your task is simple: beat levels on your first try.
When you clear a level on the first try, it adds to the total counter. However, if you lose at a level, it’s not counted towards your progress even if you beat it later.
There are three chests that you can receive: Bronze, Silver, and Gold. The more total levels you've completed on your first try, the more chests you unlock - the more valuable the chest, the more levels you need to beat, and the better your rewards. These rewards can be Coins, Boosters, Extra Cards, Extra Lives, and Undos.
Remember: the event lasts only for two days. In addition, if you open up the final chest and the event isn't over yet, you can start it again and win another batch of lovely chest goodies.