Copyright (c) 2001 Larry Back

The game is played on a 8x8 board, with the following setup:

TROIKA - A Troika is formation of 3 or more Uncrowned stones in a row, all belonging to the same player, in an orthogonal or diagonal direction.
GAME EQUALIZER - The first player must move the same stone on the first two turns.
TURN - On each turn, each player must do one of the following things (passing is not allowed):
move - A Crowned or Uncrowned stone moves to an adjacent (orthogonal or diagonal) empty cell. 
If an Uncrowned stone becomes part of a 'Troika' after moving, it becomes Crowned.
jump - Crowned or Uncrowned stones makes a double jump over two opponent stones.
Crowned stones can only jump over opponent Uncrowned stones. 
Uncrowned stones can only jump opponent Crowned stones. 
A jumping move consists of moving a stone two cells in a direction (orthogonal or diagonal) into an empty cell while passing directly over the opponent stone. After making one jumping move, a stone must make a second. The second jumping move can be made in the same direction, or in a different direction. 
Notice that a third jumping move is not permitted. 
If no second jumping move is possible, then the first jumping move cannot be made.
Jumping moves are not compulsory. All jumping moves must be double jumps.
When two Uncrowned stones are jumped then the second jumped Uncrowned stone is captured and removed from the game. 
When two Crowned stones are jumped, as long as a it would not become part a  'Troika', the second jumped Crowned stone becomes Uncrowned. If a 'Troika'  would result from Uncrowning, the second Crowned stone is captured and removed from the game.
If an Uncrowned stone becomes part of a 'Troika' after making the double jump, it is Crowned.
GOAL - Wins the player that first captures 3 stones, or makes a Crowned Troika (i.e., a Troika with 3 crowned stones).
An example

Green's move. He moves the uncrowned stone at f3 to cell [1] and makes the third crown stone (Troika at c1-d2-e3). Now Black must avoid the winning Crown Troika, but it's too late. After the forced d3-e4, green replies e2-f3, e4-d3, e3-e4 and wins on the next move!

Jumping Example

The crown stone at d6 can jump to cell [1] and then it's obliged to jump to one of the cells marked by [2], capturing the second jumped stone. However, it is not possible to make a 3rd jump over stone at e2.

Notice that the uncrown stone at e6 cannot jump other uncrown stones.

There is a ZRF to play 3 Crowns with Zillions.