When I watched it the second time, I felt myself starting to drift off in the earlier scenes and had to will myself to stay awake. I thought about what it was that made me feel sleepy and I realized it was in the darkly lit scenes (especially wearing those shades that are supposed to make it look 3D)--this was making my eyes tired, because I had to look very hard to see what was happening. I took the glasses off a few times during the movie, to give my eyes some relief, and then didn't feel as dozey after that. But I did get a headache.