Play with a travelling train, using three types of shunts.

Adam Chalcraft and Michael Greene discovered that it is possible to build a computer using a single train plus bridges and special set of shunts.
Such a set of shunts is called a 'train set'.

Shunt type 'Y': Let us start with the so-called lazy point, a Y-shaped piece of track.
A train entering the Y from below runs up the upright and out of whichever arm of the Y the points are set for, leaving them unchanged.

Shunt type 'L' (lazy shunt)
A train entering from one of the arms will - if necessary - connect that arm to the upright.

Shunt type 'F' (flip-flop shunt)
With a flip-flop shunt, trains always enter along the upright of the Y and exit through the left and right arms alternately.

The default variant shows how such a setup can be used to create a binary counter: The shunts on purple background ('flipflop right') represent the binary digit Zero, the ones on blue background ('flipflop left') the binary digit One.
Hit the run button to see how the setup counts in binary:
0000, 0001, 0010, 0011, 0100, 0101...

To drop a train or edit the board, click one of the icons on the right.
Click board several times to make them change direction.
The associated letters will remind you of what the icons mean:
T : train (default: facing north). Only one train can be on the board. The train is simply represented by a black dot on red background.
Y : fixed shunt (also called sprung point).
F : alternating shunt (flip-flop point).
L : memorizing shunt (lazy point).
B : Bend. (Note that bends and straights could be replaced by sprung shunts!)
S : Straights and crosses (crosses are also called 'intersections' or 'bridges'). You can omit them; running the train will paint straights and crosses automatically! We will demonstrate in one variant that crosses can be replaced by a set of shunts.

Please note that there are four alternative piece sets available.

Variants: please read the associated game description.

Board designs tend to be bulkier and the computing slower than in Wireworld or Photonworld because one train has to do all the work, and also because the data are represented here by static elements (namely the shunts) and not by moving elements as in Wireworld and Photonworld.

If you find interesting setups for this game, you can email them to me and I might include them in future versions of this game.

More freeware and real puzzles and games at my homepage: http://karl.kiwi.gen.nz.