Today I built out a more sturdy, efficient matrix for the magnetic sensors beneath the chess board. Lots and lots of soldering. By the end of the day I'd built three working rows.

An external view of the board with the new matrix hidden underneath. Note the eight red connectors out from the bottom (column power) and the three blue connectors out from the right (row output).

The working three-row matrix.

Another view.

Close-ups of some of the soldered switches underneath the board.

A slightly broader view.