Not sure if this is intended but a few levels before 11 the stars have completely disappeared. The good thing is that the puzzles are still solvable if you can find the most common letter placement. After making the first guess the stars are displayed for the guesses. Still loving the game so far, and I like the extra challenge.
I’m on IOS mobile browser 
Complexity varies in this way:
1) Level 1-3: the word with the guessed letters is shown at the bottom.
2) Level 1-7: the correct letters are colored in the selected words.
3) Level 1-9: the first word is selected for free.
4) Level 6+: stars show the number of correct letters in the selected word.
The next levels are on the last difficulty, when only the number of correct letters is known.
So if you see stars as on the screenshot, it's the way it's designed. I will add explanations later so that players will understand these nuances. Thank you for your attention to detail.
