kakdo°: Angle Protractor: See your iPhone Duo’s opening angle

Hi, I’m Hiro, the developer of kakdo°. I built kakdo° to put the Duo’s opening angle into numbers. The main feature displays the opening angle and its supplementary angle on compatible iPhone Duo hardware running iOS 27.1 or later. On regular iPhones and iPads, kakdo° also includes photo-angle tools. Keep several angles on one photo, add notes, save and edit measurements later, and export PNG or CSV. Photo features require iOS/iPadOS 26.5 or later. These are 2D image measurements: perspective and point placement affect the result. The gallery image shows the photo-angle tools on iPhone: measuring, fine-tuning, and saving angles in photos. US price is $1.00, paid once, with no ads or subscriptions. What would you use a Duo hinge-angle readout for?