http://www.youtube.com/watch?v=GcDshWmhF4A&eurl=http%3A%2F%2Fwww%2Evideosift%2Ecom%2Fvideo%2FMarble%2Dbinary%2Dadding%2Dmachine%2Din%2Dwood
A simple adding machine built out of wood
31+1 was the best :)
"explained more" here: http://www.youtube.com/watch?v=md0TlSjIags
lol, my first thought when I saw this, it reminded me of an old "board" game I got from Value Village that me and the kids still enjoy playing: "Avalanche (http://www.boardgamegeek.com/game/446)" (it was from the 1960s, I think :o )
more info: http://www.weddslist.com/avalanche/index.html -- and hey look a Java implementation (http://www.weddslist.com/avalanche/av.html) "The marbles never get jammed in the gates" aw but that was half the fun! ;)
PS: "Despair.com" + Board Games = punny stuff! (http://www.boardgamegeek.com/geeklist/20390/item/397505#item397505)
The urge to build this is very strong!