Any app that features 3D-thinking sparks my mind. It's too rare in our 1-D thinking world of human ignorance. (Witness: Politics).
There are three versions:
1) Free Personal version provides:
"Rapid Capture and Organisation of Ideas. Easy web-link and knowledge management. Categories and Paths. Store alternative Arrangements of ideas. Combine topics to make Networks. Create Journeys around your networks. Store your data on your device or desktop. No login required."
2) $9.17 per month (paid annually) Premium version provides:
"All Personal Features Plus: Share and Collaborate in real-time. See collaborator changes instantly.. Collaborators do not have to be subscribers.. Work online or offline. Automatic. Synchronise, Merge and Backup. Publish Spheres and Journeys to the Web.. View your private spheres in most browsers. Integrated internet picture search."
3) Enterprise version (call for pricing) provides:
"All Premium Features Plus. Manage team permissions. Team licensing. Optional on-site deployment. Optional customisation. Optional introductory courses."
[Spelling errors above not mine.]