My game has a few puzzles/challenges, and I wasn't sure how hard they were going to be to someone who hadn't designed the game. What I did is make the hard things optional, and at the end of the level asked players to tell me in the comment section how many challenges they completed. When I found out I made it too hard after the rating phase began, I dropped a subtle hint in the game description on how to solve one of the puzzles and after that people started giving more positive comments.
I'm not completely certain I have the right difficulty though. It would be incredibly appreciated if some of you could try it and tell me if I made it too challenging.