The Game of Kropki ( 'Tochki' )

Kropki is a game played by two people on a sheet of squared paper. It has achieved some popularity in Eastern Europe and Russia and can be played on a number of online web sites. Kropki is one of the games supported by the GoRilla game editor [ gorilla.html ]. This web page gives an introduction to the game.

'Kropki' is the polish name for this game. ( In russian, 'tochki' ). Some of the online web sites have given this game the translated name of 'Dots' or 'Points'. 'Kropki' is my preferred choice of name.

( Note that this is not the same as the Kropki Sudoku puzzle which unfortunately has acquired the same name. )

A sheet of squared paper is needed. The playing grid may be square or rectangular but must be sufficiently large. The players each need a different coloured pen. Each takes turn to colour a node of the grid and aims to create regions of territory that surround the opponent's points. The winner is the person who surrounds more of his opponent's points.

Regions of Territory.  A region of territory is established once a player has completed a chain of points that completely encircles at least one of the opponent's points. The points that form the chain need to connect either orthogonally with each other or diagonally across a square of the grid. When a player has formed an enclosing chain he can create a region of territory by drawing a line through the chain of points. A player is not obliged to do this immediately and may choose to do so at a later moment during the game. He may create the region of territory on any of his subsequent moves. Several regions of territory may, if possible, be drawn on the same move.

( Valid territories. )

( Invalid territory - the chain of points need to enclose at least one of the opponent's points. )

The Edge Rule.  A player may not make use of the edges of the playing grid or the corners to make an enclosure. In the following diagram White cannot create territory by playing at the nodes marked 'A' or 'B'. One consequence of this rule is that a chain of points that is connected to an edge of the grid is safe from capture

( Invalid enclosures; and a safe edge-connected chain of points. )

Inert Points.  Captured points inside a region of territory have no influence on the game. In particular they cannot be used by a player to form territory. In the following diagram Black cannot make use of the marked point to create territory by playing at the node marked 'A'. Regions of territory belonging to the opposing players cannot overlap.

( Black may not capture across a region of territory. )

However if White has not yet declared his region of territory then Black may play at the node marked 'A' and create his own territory.

( Before and after.  Black may capture because White has not yet declared a region of territory. )

Recursive Capture.  Regions of territory may themselves be captured. In the following position White can capture Black's territory if he plays at the nodes marked 'A' and 'B'. The configuration which was previously worth 1 point to Black is now worth 6 points to White.

( Capturing an area of territory, before and after. )

Mandatory Play.  Passing is not allowed.

Territorial Move Restriction.  No player may make a move inside any region of territory, either inside his own or inside his opponent's.

GoRilla is a game viewer / reader / editor for many games that can be formatted using the SGF standard [ http://www.red-bean.com/sgf/ ]. Although GoRilla was primarily written for Go, it has been extended to include Kropki.

To start a game of Kropki from within GoRilla hit Ctrl+Y, select 'Kropki' and choose a board size.

GoRilla is a compact, non-commercial program ( freeware ), and is available from my web page [ gorilla.html ]. I hope you will find it a useful product.

[ http://en.wikipedia.org/wiki/Dots_(game) ] Wikipedia page for Kropki / Dots.

[ http://kropki.nongnu.org/ ] A freeware program that can be used to play the game.

[ http://eidokropki.reaktywni.pl/ ] An implementation of Kropki based around the EidoGo software that has been developed for Go / WeiQi.

[ http://www.kropki.legion.pl/ ] An online forum for the game.

[ http://zagram.org/kropki-rules.html ] Another useful site.

[ http://igg.me/at/dotsbook ] DotsBook. A project to deliver a Kropki online app for IOS and Android.

[ http://openkropki.sourceforge.net/ ] OpenKropki. An open-source, multi-platform implementation of the kropki game with an SDL2 UI.