Windows app download link:
https://www.microsoft.com/en-us/p/notedex-index-cards-and-notes/9mvflmts597h
Mac and iOS app download link for Mac, iPhone, iPad
https://apps.apple.com/us/app/notedex-index-cards-notes/id1513493654
Android App download link:
https://play.google.com/store/apps/details?id=com.sat.notedex
Don't forget you can also use the full app on the web: