The current set of Logic Goats includes an and-goat, a not-goat and an or-goat. As all computer geeks know, we're missing the exclusive-or-goat or xor-goat.

In the current goats the goat nods its head depending on which of the keys on the front of the box is pressed. The and-goat nods when the left AND the right button are pressed. The not-goat when the single button is NOT pressed and the or-goat nods when the left OR the right OR both buttons are pressed.

There's a YouTube video of the current logic goats here.

The goat that has eluded me so far has been the xor-goat. In this model the goat nods when the left button is pressed OR the right button is pressed but not when both are pressed.

So… while watching New Moon with my True Love I was idly toying with a water bottle top when I worked out how I could make the elusive xor-goat. The picture shows a second draft for the internal mechanism.

The circled part on the top frame is connected to the goats head. If it turns from the horizontal the head nods. Top frame and bottom frame the piece is horizontal so the head is up. On the two middle frames, left button OR right button is pressed and the head nods. Ha!

I have a few more changes to make before I add an actual goat to the mechanism but it is certainly coming on!