The course at that site is pretty interesting. There is an error that doesn't affect any of the examples but might be a problem for future circuits: what are ca

The course at that site is pretty interesting. There is an error that doesn't affect any of the examples but might be a problem for future circuits: what are called OR are actually XOR. It took me a while to figure it out because the notation for "don't care" was not obvious to me (it was explained later in the text after table circuits are introduced). I was able to build a circuit to test this by copying an OR to the display block and hooking up the inputs to the buttons and the output to column 1. It might be interesting to have some scheme to test sub-blocks directly.