This is a new feature that our game team has recently added, where stars are added based on the number of attempts you've taken to complete a level, and not on the points you earn during the level; 3 stars for the first attempt, 2 for the second, and so-on.

If you're noticing a difference in the stars between older levels and newer levels, this is due to the game not updating the level of stars for previous levels, because these would be based on point count. All new levels will award stars based on the number of attempts, but the game won't update older levels completed previously to reflect this.

We're sorry if this has caused any confusion, but if you have any other questions, we'll be happy to help: you can open a support ticket here.