## Help For the Game Of Y

### Introduction

Welcome to the network Y server. The rules of Y are below. The Y "challenge" command is described here. Other commands are the same for all pbmserv games.

y challenge [ -size=N ] userid1 userid2
Start a new game between userid1 and userid2
N specifies the size of one side of the playing field. The default size is 17.

Note that Y only supports games with just two players.

### Y Rules

```

1- .
2- . .
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\ \ \ \ \ \ \ \ \ \ \
A B C D E F G H I J K

Diagram 1
```

Y rules:

• The playing field is a triangular grid. The game starts on an empty board. Players (X and O) move in turn to place one stone on an empty cell. The first move is made by X.
• The game is won by the first player to build a chain of stones of his color which connects the three sides of the playing field (see Diagram 2 for an example of a winning chain).
• A corner cell counts as belonging to two sides.
• After the very first X is placed on the board, O has the right to swap sides (see swap command). This rule prevents X from playing to the center of the field at the first move and getting in this way a strong advantage.
```

1- .
2- . .
3- . . .
4- . . . X
5- . . . X .
6- . . . X . .
7- X . . . X . .
8- . X . X X . . .
9- . . X X . X . . .
10- . . . . . . X . . .
11- . . . . . . . X . . .
\ \ \ \ \ \ \ \ \ \ \
A B C D E F G H I J K

Diagram 2```

### Background

Y was invented by Charles Titus and Craige Schensted. Besides the version implemented on this server, several other versions of the game exist. They differ by the size and shape of the grid. In one popular version there are three special internal cells in the grid, which are connected to only five other cells (unlike a normal internal cell which is connected to six other cells).