Hoth 3-21 is the twentiy-first level in Hoth episode in Angry Birds Star Wars. In this level, Chewie gets his upgrade where he becomes stronger.
Getting 3 stars in this level required ONLY one bird. It's extremely hard to do it. Target score is very high.
You can often miss 3 stars even you use only one bird.
The northern pig on the rightmost planet is extremely hard to pop.
Overall, you need a massive luck to win this level with three stars.
Getting 3 stars is very hard.
Send Chewie toward the large northern asteroid, barely clipping the icy asteroid in the way. The shards of the asteroid should fall onto the northern planet, while a piece of ice drifts into another, into the other large asteroid, and hopefully onto the eastern planet. A one-bird clear should earn you three stars if you are lucky enough.