The app must be completely usable with the standard 2-sensor desk set up.
The app must provide a way for users to pick up VR objects on the ground even if the desk occludes the sensors.
The app must not require users to interact with content behind them. If you place content behind the user, the app must take steps to keep the user facing frontwards to avoid occluding the sensors with their body.
The app must provide interactive content behind the user.
If the app is roomscale, the app must be completely usable with the 3-sensor setup.
If the app is not roomscale, the app must be completely usable with the 2-sensor 360 experimental setup.