[ant6n]

This is very neat. When playing with this set, I've wondered about this.

...

It seems the text says for 12 pieces there are 2 solutions, but the animation shows four.

Also, there doesn't seem to be a check to see whether the bridge pieces are together. (When all 's' pieces are used there has to be at least one connected pair).

[mcconnma]

Thanks. I updated the code and the post to reflect tests for the bridge case as you mention. It affected the 12 piece and 16 piece solutions. The animated gifs are udpated and should be correct now.