8x8 array of photoresistors (or similar)

So, I found myself lost when trying to implement a cheap way of detecting movement on a 8x8 array (64 different spots).

As you might've guessed, we're talking about a chess board here, a transparent glass chess board.

At first I was going to do it with something like a webcam on top of the board and RoboRealm doing the motion detection.

Then I realized that using 64 photoresistors would also do the trick. Then again, I'd need to find out how to make an array out of those so I wouldn't need 64 I/O pins. Photoresistors are also kind of expensive.

My question is, does anyone have any ideas to contribute? :)

The way to do it would be to use two 8 to 1 analogue multiplexers (4051). One would supply a pulled up to 5V through a resistor onto the rows (one end of the photo resistor) and the other would select what column (other end of photo resistor) gets routed to the analogue input.

I see, I saw some discussion about multiplexers before.

How about using LEDs ("LED touch sensing") to achieve the same?

There's only two different options/phases I'm looking for and those are when the LED has direct contact with a light source through the transparent board, or when a chess piece is blocking the light on top of it.

(the chess pieces have a black piece of cloth taped on the bottom of them)

I wouldn’t bother with using an LED to sense the light, I have done some tests with that and it is not reliable when you use a matrix.

You could use a reflective optical switch and have a white label on the base of the chess pieces.

The other way is that you could have a hall effect sensor and a small magnet on the underside of the piece. The cheapest hall sensor I have come across is about £0.50. What ever you use multiplying by 64 makes it expensive.