WARNING!! The app WILL eventually stop working and the developers do NOT respond. The problem in "Stem Changes' is well known and has not been addressed. No option to actually complete the exercise. Dead in the water. Update: when the app stops you, you can get past the programming error by switching to the mobile version. I would NEVER pay for this problem laced app with no support. Idiots keep pumping out updates but don't fix the problems with previous updates. 🖕