Copyright (c) 2003 Bill Taylor

The game starts at following hexagonal board (the marked stones belong to First player, the others belong to Second):

MOVE - On each turn, each player may do one of the following actions:
Move a friendly piece by sliding any number of empty cells in a straight line.
The moved piece must end up geometrically closer to at least one enemy piece.
Capture an enemy piece. Capture is mandatory but the player may chose between options. There are two ways of capturing:
Replacement - moving onto an adjacent enemy piece, thus removing it.
Whistling - making a valid slide and any capturable enemy piece which was adjacent to the line of movement, but not adjacent to the starting or finishing cell, is removed. 
When whistling, red captures white, white captures blue and blue captures red. These are the only valid whistling captures.
GOAL - A player loses when he has no pieces left.
An example

Second's turn. He moves his red stone from a7 to [1], capturing white b3. First is forced to capture it (by replacement) with the white stone at b1. 

Then Second whistles f4 to [2] capturing two blue stones. First is forced again to capture that stone.

Second was able to capture three pieces in exchange of two pieces of his own. 

This game was derived from the 3 player game Triad from Cameron Browne.