What cool project can you do if you have a Raspberry Pi Zero and a Projector?

How powerful is the projector? Could you display something on the side of a building at night?

Take a picture of the outside. use the raspberry pi to project it onto the wall. Also you can use the raspberry pi to project various bit patterns onto 3D surfaces and then by identifying the 3D pixels you can capture 3D surfaces.

Create a Chess or Go coach that projects attack lines or shows the future strength or vulnerability of positions on the board.