Interval Timer: HIIT Workouts.

Using an iphone X… The app doesn’t have any sort of chime or sound notification, so the only way to know when to switch between stages of your workout is to be looking at the screen. But the app doesn’t keep the Lock Screen from coming up, so that watching the clock isn’t even an option. Useless.

I was in a pinch and downloaded this to use for a run. No matter what I did, the start button wouldn't brighten so I could press it to work. I even had others try to make it work, no luck.