Implo 2020

Implo is a finite territory game for two players: Black and White. It is played on the intersections (points) of an initially empty square grid (board). The recommended board sizes are between 6×6 and 10×10 points. Each player must have access to a sufficient number of stones and markers of their own color.

DefinitionsIn these rules, "adjacent" always means "orthogonally adjacent".

A group is a piece along with all other pieces one can reach from it through a series of steps onto identical adjacent pieces. Thus, all pieces in a group are the same type (stone or marker) and color (black or white).

The size of a group is the number of pieces in it.

Likewise, a territory is an empty point along with all other points one can reach from it through a series of steps onto adjacent empty points.

A patch is a territory including at most four points.

The owner of a patch is the player with the biggest group of stones adjacent to it. If there is no such group or the biggest such groups of both colors are the same size, the owner of the patch is the opponent of the player who placed the last stone on the board.

To resolve a patch is to place a marker of its owner's color on each of its points and to remove the biggest group of stones that is adjacent to the patch and owned by the same player as the patch. If several such groups are tied for biggest, the player who is resolving the patch removes, among those, one of their choosing. If there are no groups of stones adjacent to the patch, no group is removed. Note the player resolving the patch need not be the owner of the patch.

PlayBlack plays first, then turns alternate. On your turn, perform these actions in order:

Place a stone of your color on an empty point of the board. Resolve any single patch on the board. Repeat the previous step until no patches remain. Note the order of resolving matters, and resolving a patch may create new patches.

If, at the end of a player's turn, there are no empty points on the board, the game ends.

The winner is the player with more groups of markers of the largest group size. If there is a tie, the player with more groups of markers of the second-largest group size wins, and so on. If it is tied all the way down, whoever has more stones on the board wins. If this is also tied (only possible on even-sized boards), whoever made the last move loses.

To make the game fair, White will have the option, on their first turn only, to swap sides with Black instead of making a regular move.