eg Say for a levelset you have completed 10 out of 50 levels then the number 20% or a progress bar at 20% would be displayed (on the menu screen). And when it gets to 100% a smiley face is shown next to it or something.
This might encourage people to try and complete more levels to try and up that number rather than just skipping ones they find boring/too hard.
I've said this before but I still think when you complete a level and it asks you if you want to replace the current tape it should tell you if you have beat the time of the current tape (many users may want to keep a tape of their best time).
Couple of small ideas
Moderators: Flumminator, Zomis