GOAL
Find the holes in your opponent's secret pipeline before he finds the holes in yours. The pipelines are probed by adding colored liquid and seeing where it goes. Both pipelines are probed simultaneously, so getting information about your opponent's pipeline also reveals information about yours.
EQUIPMENT
- paper and pencil
- 4x4 square board
- 8 pawns: 2 blue, 2 yellow, 4 white
- 2 coins
- optional: 40 tokens: 8x blue, yellow, green, black, white
SETUP
The players are called Head and Tail. Head puts the head coin on any square. Then Tail puts the tail coin on any other square. The coins specify the head and tail of the secret pipelines.
Each player draws a pipeline on a paper grid that's kept hidden from the other player. A pipeline is any path of adjacent squares that goes from head to tail without visiting any square more than once. It can be marked with a continuous line that doesn't cross itself. It doesn't have to use every square, but it must be at least 3 squares long, not including the head and tail.
Each player also marks 3 squares of the pipeline, which are the holes. Holes cannot be in the head or tail squares.
The pawns are a system of probes, and any pawn can be moved by any player. All pawns are initially off the board, and they get placed on the board by moves.
GAMEPLAY
Players alternate turns. Head moves first. On your turn, you can either make a guess or do a probe.
Guess
To guess, indicate 3 squares on the board, which is where you think your opponent's holes are. If you're right, you win.
If you're wrong, the game continues, and you can't guess again right away. You have to do N probes before guessing again, where N is the number of wrong guesses you've made.
Probe
To probe, take any 2 pawns from anywhere, and move each to some square on the board. No square can have more than one pawn. The move must change the board. You can't put a pawn back where it came from, and you can't just swap two same-color pawns. You don't have to move a pawn onto the board if there's some other move available. Once a pawn is on the board, you can't move it off.
The pawns on the board are a probe configuration that gets applied to both secret pipelines. The two pipelines are independent of each other, they're probed separately, but both probes use the same configuration.
After you move the pawns, you tell your opponent what the probe reveals about your pipeline, and your opponent tells you what it reveals about their pipeline.
This is how the probe works:
The blue and yellow pawns are sources of blue and yellow liquid. If a pawn is on a square that isn't in the pipeline, then the pawn doesn't do anything. Otherwise, colored liquid enters the pipeline at that square and flows toward the tail as far as it can.
The pipeline is one-way. There are valves at the edges of the squares, so liquid always flows toward the tail and never flows toward the head.
Liquid will enter a square with a hole, but it doesn't continue past that. (It gets sucked out the hole.)
When blue and yellow meet, the liquid becomes green, but only from that point forward.
The white pawns are detectors that tell you the color of liquid in that square. There are five possible results: miss (no pipe), empty (no liquid), blue, yellow, green.
If you have colored tokens, use those to mark the results at each white pawn. See the diagram for an example.
DIAGRAM: greenpipe.jpg
