Idea/solution for building target to detect nerf dart accuracy?
A flexible transparent resistive touch panel could be the answer to your design problem. This kind of panel might be able to cope with the dart impact force, and will give you a reading from which you can calculate the XY position of the contact point.



Resistive touch panels are 4-wire analog sensors need to be interfaced through circuitry including ADCs, clocks and special-purpose controllers. However, this circuitry is commercially available as breakout boards, not too expensive, and some of them come with USB interface for extra convenience.

The main challenge could be finding a panel with the size required by your application, but reasonably priced as well. Only you know your budget constraints!

As an example: 17-inch panel with controller.