It's free, please try it at: App Store: https://apps.apple.com/app/y-a-p/id6744711983

Google Play: https://play.google.com/store/apps/details?id=ex3.yap

For more technical details, please read my blog: https://benwu232.github.io/posts/virtual-knobs/

https://medium.com/@benwu232/virtual-knobs-making-human-mach...

https://dev.to/benwu232/virtual-knobs-making-human-machine-i...

Please have a try and let me know what you think! Thanks!