I am making plans for my next PND Game. Would you rather a Super Mario Bros type of game or a tower defense game?
Have you seen Intake? It would be an amazing game for you to do something PND with.
https://www.youtube.com/watch?v=6P1y4dpSeJMYou have to switch back and forth between 2 colours with the RMB, and you have to hit the ''pnds'' accordingly with the LMB. Addicting dexterity game that's a thrill to play.
To add to that it also has an ''upgrade'' mechanic where you score points on the side to get different unlocks/powers (maybe something players can spend their won PND on? It might lower the strain on community donation driven games)