ORBIT

Copyright (c) 2000 Steve Meyers

Orbit is played on an empty 16x16 square board:

TURN - On each turn, each player drops a stone into an empty cell. A player may pass his turn (if both players pass, the game ends) PIE RULE - One player drops two black stones and one white stone. The other player decides which color to play.  CONNECTION - Two friendly stones are connected if they are orthogonally adjacent or diagonally adjacent. ORBIT - An orbit is a connected set of stones which completely encircles one or more cells. When an orbit is formed, any enemy stones within the orbit are removed from the board, and it is thereafter prohibited for the opponent to play within that orbit. HALF-ORBIT - A half-orbit is a connected set of stones which, together with one side of the board, completely encircles one or more cells.  When a half-orbit is formed, it is thereafter prohibited for the opponent to play within that half-orbit (but enemy stones inside are not captured). ENDGAME - At the end of the game, any stones that cannot avoid capture are automatically removed from the board.  There is often the existence of some shared territory (cells where both players are prohibited from playing). GOAL - Wins the player with more territory, meaning the number of empty cells he controls exclusively (there are no points for shared territory, captured stones or stones onboard.).

Some examples In the top left corner, black is not forbidden to drop, since white does not have a half-orbit (the stones connect two adjacent edges rather than a single edge to itself). On the left side, if White plays the marked stone, he will create a half-orbit, forbidding black to place any stone within (and securing that territory), but the black stone is not captured. In the bottom, white manages to create an orbit (by dropping the marked white stone) and thus captures two black stones and secures that territory!

Some words from the author:

there is no Ko in Orbit, the reason being it is prohibited to play within an opposing structure. For the same reason, "invasion" is not possible in the usual sense --- however, a portion of or all of your opponent's structure can sometimes be destroyed, meaning that it is now permissible to play within it since it no longer exists. (BTW, it is permissible but never advantageous to play within one of your own orbits).

More information can be seen at Meyers' website:

In general terms Orbit is a family of 29 Go-like games, all of them playable but some more intriguing than others. The version given here as standard was described in Issue 12 of Abstract Games. It also appeared in November 2001 Games, where it was called Half-prohibition Orbit. (The essential rules can be summed up as, "Half-orbits prohibit, orbits capture and prohibit.")

Although stones are captured during the course of the game, Orbit can still be easily played with pen-and-paper. The reason is that captured positions are not subsequently re-occupied --- it is illegal for the captured player to do so, and it is a wasted move for the capturing player to do so. Orbit probably isn't as graceful of a game as Anchor, but if you're the "hardcore" type who likes a maximum challenge, then I think there's a good chance you'll enjoy it.

Addendum: In case anyone's curious, I thought I'd go ahead and briefly describe the full Orbit family. There are 26 "nuts-and-bolts" variants and three special variants. In Orbit there can be up to three kinds of structures: quarter-orbits, half-orbits and orbits. A given structure can function in one of two ways: prohibit, or capture and prohibit. If you take all the permutations of the existence and non-existence of the structures, and cross that with the two function choices, you get 26 variants. The standard game and "quarter-prohibition Orbit" are among these. The first special variant is Conversion Orbit, which I've renamed conversion Go. The second special variant is the "torus" variant: a regular board is used with the understanding that the left and right sides are connected, and the top and bottom sides are connected. There is only one rule: orbits capture and prohibit. (If you decide to try this one out sometime, remember the following important fact: an orbit is only valid if it is inherently self-connected --- a self-connection resulting merely from the toric nature of the playing area is not a sufficient condition.) The third special variant is as follows: half-orbits prohibit, orbits capture and prohibit --- but all outside liberties must be filled. (Inside liberties do not need to be filled.) So in this variant the mechanism of liberties is partially adopted.