Geometry DashDifficulty levels parallels Osu very closely, except Hard is split into two parts (2.25-3.00 stars, and 3.00-3.75 stars). Demon (Expert / Extra) have 5 separate difficulty icon based on the star rating.
Star Ratings are for Osu, not Geometry Dash.
Easy (under 1.5 stars, as per Osu ranking criteria)
Normal (1.5-2.25 stars, as per Osu ranking criteria)
Hard (2.25-3.00 stars)
Harder (3.00-3.75 stars)
Insane (3.75-5.25 stars, as per Osu ranking criteria)
Easy Demon (5.25-6.00 stars)
Medium Demon (6.00-6.75 stars)
Hard Demon (6.75-7.50 stars)
Insane Demon (7.50 - 8.25 stars)
Extreme Demon (over 8.25 stars)