My windshield seems to have two visible areas, the one swept by the wipers and all the rest. You can clearly see them when you look across it at an angle. I've never been able to really clean the glass so that it is the same overall. I found this video and it seems to be the OCD Guide to Cleaning Glass, but I want to give it a try. Being able to see well, especially in bad weather, is critical to safe driving.