I found the program that this project is based upon in the sample programs library of the Berkeley
Snap! programming tool.
It uses two forward-facing 'sensors' that test the Canvas BackgroundPixelColor at a specific x,y locations to guide a quadcopter around a white path.
The paths alternate between voilet and green to show that it can follow different paths.
A nice enhancement to this would be to add more paths or to allow the user to create a path.


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sf