Stars reflect how well you win, not just whether you win. 1 Star: Win the level (finish in 1st place). 2 Stars: Win by a comfortable margin over 2nd place. 3 Stars: Dominate — win by a wide margin over 2nd place. If you don't finish in 1st place, you earn 0 stars. The exact point thresholds for 2 and 3 stars scale up with Kingdom difficulty.