The main problem with this is collecting the stars takes the user's attention away from the product and turns it into a focus on the game. So in the very first impression of your product, the users aren't taking in your product, they're looking for stars. Seems like a very narrow focus of their attention that will lead to missed context.
It's a tough one - usually the regular "tooltip" approach is used, but I find myself skipping through them all. With the star approach, I found that I was exploring the UI more until I found the star and revealed a tooltip.
No idea if the approach works well generally though. Highlighting important features in a complex product is a tough problem to solve!