There are simple video-editing apps, and then theres Fly, a new iPhone app that lets you edit a short movie inside literally one screen. You can add a voice over or background music from your device, and then export your video to post on Instagram or elsewhere. The apps unique mix of simplicity and clever features for power users could give it an edge in a time where video editing apps are finally hitting it big on mobile. Only with the rise of Instagram Video and Vine have any of these apps actually caught on. Flipagram attracted millions of users with its clever take on photo and video montages, PicPlayPost let you post diptics of photos and videos inside the same frame, and Videoshop let you add sound effects and voice overs to your clips before you post them.