The Project SPECTRA! app is a set of interactive lessons to help students learn science topics, particularly how light is used to explore the Solar System. It is meant to be an in-classroom activity, accompanying lessons found here:
https://lasp.colorado.edu/home/education/k-12/project-spectra/

The app features interactive activities for 11 different lessons. Some of the activities serve as alternatives to purchasing scientific equipment to use in the classroom.

For an accessible version of the app, see the above link.