The object of Shacru is to acquire as many squares of your color on the board as possible before the game is over. The board is a 9 by 9 grid divided into 9 borderlands of 3 by 3 squares (could now be mistaken for Sudoku!), and at the start of the game all of the squares are neutral (not colored).
With 2 players there are four pieces (aka chevrons) each, with 3 or 4 players three pieces each.
Each time you move a piece the square you move onto becomes your color. You can move onto neutral squares, or squares of your own color, but not onto squares of a different color. So the game focuses on blocking the pieces of other players, and avoiding your pieces becoming blocked.
Pieces move only forwards (forwards directly or forwards to left or right). When a piece crosses a border the player can twist the piece 45 degrees to the left or right.
The game ends when no player can gain any more squares of their color (either because none of their pieces can move, or because they can only move around onto squares that are already their colour).
Shacru was first published as part of the Pacru 101 game, and again with the Pacru 302 game. It can also be played with crayons and paper with the addition of some colored chevron/arrow shaped pieces to move around the paper. Free software exists at http://www.pacru.com/shacru.html.
The game is suitable for anyone aged five years or over.
Separate entries exist for Pacru, Shacru & Azacru as opinions vary widely on the 3 games.