I know almost nothing about operating my Nexus 6 phone, but the camera worked before. Now, when I open the camera, the top 90% is black; 100% of the background is black. There is a camera icon with two circle arrows around it on the left, and a big circle in the middle. And three icons for exiting the app. Pressing the circle turns it blue while I press it, and that's all. I tried clearing the camera app cache.