I just rechecked the app and tried out the free HVAC sim and it was great. It would be better if one had the option to teleport or slide to the area if they didn't have a large a space as might be needed for the sim. Downside, its costly and after a certain period you have to "renew your subscription" if you want to gain access to the learning materials again so it seems as if its more like a rent for a time tuition imo.