I want to build a megalithic computer using a river flowing down a mountain. The AND gate is a enormous door lifted by an enormous arm attached to an enormous b

I want to build a megalithic computer using a river flowing down a mountain. The AND gate is a enormous door lifted by an enormous arm attached to an enormous block hollowed out from the bottom so that it can float. Input is done by almost lifted doors that can be moved by applying enough man power. The display is just enormous blocks lifted up. It should do something important like play pong.