Do you mean some little doors on the road? if so, it is about the winter harmony; you must reach the levels where they are and Tiffi is giving you bossters and in the last door it gives you more than in the previous ones. Greetings.
or if you refer to the gift box that appears above the boosters when you start each level; carries a candy counter with the letter c; that when it is lit at the level that you play, those candies appear with a letter c and when thundered they accumulate on the left side of the bowl; You must be online to be exchanged for boosters or gold bars. to me that green box sometimes appeared blue. or dream it . Grettings.