Backgrounds for wallpapers are loading through the open API https://api.nasa.gov.

Server api: Firebase (firebase branch) / REST api

• Glide
• Room
• JetPack Navigation
• LiveData
• Work Manager
• Wallpaper service
• SensorManager
• CoordinateLayout

Images from: https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY

Install application from: https://play.google.com/store/apps/details?id=com.devapp.nasawallpaper