Yodd, the hexagonal version of Xodd, is a 'dynamic goal' connection game invented by Luis Bolaños Mures in 2011. It is played on a hexhex board of arbitrary size, but base 6-9 are recommended.

Terminology
  • Group: a set of connected, like-colored stones on the board.
  • To drop: to place a stone on any empty cell.

Yodd boardRules
The game starts on an empty board. There are two players, white and black.

  • Starting with black, players take turns dropping one or two stones of any color. On his first turn, black can only drop one stone.
  • At the end of each turn, there must be an odd number of groups on the board.
  • Players can pass their turn at any moment, unless it violates the previous rule (this means black can't pass on his first turn).
  • When both players pass in succession, the game ends. The player with less groups on the board wins. Draws are not possible.

Note that there's no actual counting involved in the non-parity rule: just keep it odd.

Examples
The position on the left side of the board shows 5 groups total. If a black stone is dropped at 'A', there will be 2 groups less on the board, so parity doesn't change. On the right side a legal move for any player has been made. Note that the second placement doesn't change parity, either.
The position on the left side of the board shows 3 groups. Dropping a black stone at 'A' reduces the group count by 1, so the total number of groups will be even. The second move of the turn must change the number of groups back to an odd number, as is shown on the right.
On his turn, black would like to join his two groups by playing black stones at 'A' and 'B', but he can't. That would reduce the total number of groups to 4, and he would need another move to restore the group count to an odd number.
Here both players have passed. Black has 2 groups to white's 3, so Black wins. Note that White can't join his groups at 'a' because there is no way to restore the group count to an odd number afterwards.
The diamond connection is still unbreakable, unless the opponent can fill the intermediate cells by growing one existing group at one of the marked cells.


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Using the Xodd applet
External links

Yodd © Luis Bolaños Mures
Java applet © Ed van Zon