*Keil* is a Go-like game for two players, Black and White, played on the spaces _(cells)_ of an initially empty hexhex board (or, equivalently, on the intersections of a hexagonal grid of triangles). It preserves crosscuts and ko thanks to the idea of coupling cells, which reduces the natural connectivity of the board. Otherwise, the rules are the same as in Go. In particular, the concept of domain performs the same functions as the concepts of group, liberty and territory in Go.

*Definitions*

Two adjacent cells are said to be _coupled_ if there is a third cell adjacent to both such that the three cells together contain 0 to 3 stones of one color only.

A black _domain_ is a set of mutually coupled cells containing one or more black stones, one or more empty cells and no white stones. Likewise, with colors reversed, for white domains.

*Play*

Black plays first, then turns alternate. On your turn, you must _pass_ or _place_ a stone of your color on an empty cell. After a placement, remove all enemy stones which don't belong to any domains. After all removals, the stone you placed must be part of at least one domain, and the current board position must be different from the board positions at the end of all your previous turns. Otherwise, your placement was illegal.

The game ends when both players pass in succession. The player with the higher score in the final position wins. A player's _score_ is the number of cells belonging to their own domains only, plus a komi in the case of White.

_Finished game. Black won by 0.5, with 67 points to White's 66.5. Komi was 6.5 points._

(Sorry for the formatting mistakes) :/