The Festive Adventure
Birthday hats are required so many people should have these already.
Total of 9 rounds with rewards of a rare chest after round 1, 1,000 feathers after round 3, 2000 feathers after round 5, 5,000 feathers after round 7, and 10,000 if you finish round 9.
1 and 2 are easy if you have all the birds. Four and five gave me all kinds of trouble, and six is probably where I'm done. It's a lava round so it completely requires 100% luck to have not only debris land just right, but also the rock shooters to take out unreachable structures with their first activation. I couldn't get past room 2 except once and quickly quit on room 3 when it went no where.
If I had to guess probably starting on round 7 it will be 7 rooms, and would not be shocked at all of rounds 8 and/or 9 are 8 rooms.