Principle Mirror is a free iPhone app developed by Daniel Hooper. It is a companion app to Principle for Mac, designed for designing interactive interfaces. The app can open Principle files from other apps or mirror Principle for Mac when plugged in.

Principle Mirror is a tool that can help designers and developers in creating and testing interactive interfaces. It is a free app that is easy to use and can be used on the go. The app has received positive reviews from users, with some describing it as amazing and well done.

Overall, Principle Mirror is a great companion app for designers and developers who use Principle for Mac. It is a useful tool that can help users create and test interactive interfaces on their iPhone.