The Ul was a bit unintuitive at first—pushing Play when you pause using your Aligner, and pushing Pause when your Aligner is back in play—but once you wrap your head around that, it's easy to use, and the use of concentric circles to visualize how you're doing each day is similar to the Apple Health app model.I'd love to see the play/pause paradigm reversed to match media players, and it'd be a bonus to have a Watch app, but what's here works really well. Note that there is no cost and there are no in-product upsells, just some nonintrusive banner ads along the bottom of the screen. Overall, I like it much better than the Invisaligner and TrayMinder apps.