Once I understood that I just had to look for the next light, it became a very straight forward exercise. The 'invisible' path was brilliant! I really like the screen effect you used here. It feels like the invisible road appeared at the exact moment that following lights scattered about became stale, which is a testament to good pacing. Following down the path wasn't hard at all, but it became a little boring by the time I'd reached the bottom, as I got used to the effect. I don't think just shortening it would do it any good though. Perhaps making it more of a challenge to descend the path could solve that issue.