Everybody loves abstract wallpapers and free stuff, right? I installed a new app called Spectre on my iPhone. It’s made by the same guys behind the Halide app. Which is, right now, one of the best camera apps for smartphones. But Spectre’s purpose is to help you with long-exposure photography. So you won’t find it if you look for something to create abstract wallpapers. I mainly use it when I’m out, to...