Actually there
are some examples of water based "logic gates".
But when I last looked at them, it was hard to see how they worked.
In the latest version of minecraft, a guy built something he called the Commandore computer.
https://www.youtube.com/watch?v=go5qdMKZs-MHe uses "scoreboard scripting" which was added a couple of versions ago. So most of the action of the cpu is hidden in script code.
But he uses an interesting technique, employing a new addition to Minecraft, namely moveable "conducting" Redstone Blocks. There are script commands to let you move / create / destroy these blocks.
But the script commands have an awkward syntax, such that there is limited "variable substitution" allowed. Therefore he has "hard coded" one "scanner block / command block" for each of the 256 memory slots, with an empty "air gap / block" between the row of scanner blocks, and a row of "trigger / command " blocks.
As the minecraft redstone "clock" fires, the command blocks create "conducting" Redstone blocks (all 256 at once (or was it two blocks of 128 .. I forget), and the one possible value is detected by the associated trigger block.
Surprisingly with all the over head / layers of abstraction, the CPU runs at ~30 Hz or so
He has also created a color "graphics" "GPU" with redstone / command blocks.
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There is also at least one mod that I played with a while ago, that has water wheels, which I was hoping to use. I made some basic progress with them, didn't get as far as any logic gates though.
The water wheels only interacted with redstone "electricity", though. I am looking for something that is mechanical.
I also played with a Steam game, called Gary's mod. Last I looked at it, it had some better physical things than Minecraft (balls dropping on levers, etc). I didn't get too far with that either.
Rather than "obey" the "laws" of these games, I've also experimented with some 3d animation stuff, to try to illustrate low-level cpu architecture.
Mike