I came across "Learning XOR: exploring the space of a classic problem" other day: https://www.maths.stir.ac.uk/~kjt/techreps/pdf/TR148.pdf https://www.maths.sti

I came across "Learning XOR: exploring the space of a classic problem" other day: https://www.maths.stir.ac.uk/~kjt/techreps/pdf/TR148.pdf https://www.maths.stir.ac.uk/~kjt/techreps/pdf/TR148.pdf Even something with three units and two inputs is nontrivial to understand on a deep level.