The Chess Variant Pages

Outer Space Chess

By Nicholas Kuschinski


Outer Space Chess is a themed chess variant developed for the 43 square competition.

The idea of having two different boards came mostly from the impediment caused by 43 being a prime number. The elements of Outer Space Chess come from all over the place. An interesting source of inspiration (that I found a little too late, after many of the rules had been defined) was Hitchhiker Chess, from which I got some of the ideas about piece movement. Other people who want to enter this contest might want to look at it for board design (just replace the black hole in the center with another square). I'm pretty sure, however, that the final pieces (with the exception of the Planets, taken from Standard Chess), are completely unique. So far as I know, the Galaxy-Nebula system has also never been used before. Other sources of inspiration included Ultima and Nemoroth for defining the movements of spaceships, several 3D variants that involve multiple boards (mainly Dragon Chess) Also, some ideas have been taken from Xiang Qi, and Congo, mainly with respect to the Nebula. It is not necessary to know the rules to any of these games in order to understand this document, although familiarity with some of them might help.

Familiarity with Orthodox Chess is assumed, but much of the game is described from scratch. If you don't know Orthodox Chess you might want to look up Knight, Rook and King movement, as well as stalemate, and it is probably also a good idea to be familiar with the turn-by-turn game system, which can be learned not only from Chess, but also from Checkers, Chinese Checkers, etc.

The outer space theme eventually turned out to be rather unrelated to several aspects of the game, but in the beginning, it looked like everything was going to fit in perfectly. The space theme stuck, however, because I didn't see any reason to get rid of it.

Hyperspace is a board consisting of only three squares, but as will become apparent from the rules, it is an extremely important strategic element, and the control of these three squares is a determining element in the game. The discussion of strategies and tactics at the end is mostly about how hyperspace and Black Holes affect the game. The rules about leaving hyperspace, as described, might seem a bit foggy, so I will also go into details about this. Other than this, I will only give pointers about the endgame, and how the Galaxy-Nebula system works. As well as a couple guesses about piece values.

The game has not yet been playtested, so most of my discussion will be coming either from rigorous analysis, or from the strategies that I tried to embed into the rules. Although no obvious flaws are present. If anyone finds any, feel free to comment, or alternately, send them to me (click on my highlighted name below to send me e-mail).

The Game

The game of Outer Space Chess is played on two boards, one of which is 5x8 squares and the other consisting of three squares end-to-end. Henceforth, the larger 5x8 board shall be called ordinary space, and the smaller three square board shall be called hyperspace. On ordinary space there are be 6 markers (positions of these to come later) which are called Black Holes, as well as one on the central square of the three square board.

Two players shall each make a move in turn. Play continues until either one of the two players loses (be that by losing his nebula or by resignation) or until a draw is reached. Rules of time, of etiquette, of takeback, etc. shall be determined by whatever method is considered appropriate.

The Pieces

Each player has at his disposal 10 pieces, consisting of five Star Clusters, two Planets, one Spaceship, one Nebula, and one Galaxy. These pieces shall be colored, painted or shaped in such a way that it is easy to determine which player a piece belongs to and what type of piece it is. It is suggested that the shape of these pieces be suggestive of the name of the piece, and that the two sides be colored black and white. If the pieces are made as suggested, the White player shall move first; otherwise, the player to move first shall be designated via whatever method is deemed appropriate.

The Array

For this diagram, a * symbolises a Black Hole, a - represents an empty square, a C represents a Star Cluster, a G represents a Galaxy, an S represents a Spaceship, a P represents a Planet, and an N represents a Nebula. Lower and uppercase letters are used to differentiate the white from the black pieces.

Ordinary space: Hyperspace:
8  | C | P | N | P | C |
7  |   | C | S | C |   |
6  |   | * | C | * |   |
5  |   |   | * |   |   |
4  |   |   | * |   |   |
3  |   | * | c | * |   |
2  |   | c | s | c |   |
1  | c | p | n | p | c |
     a   b   c   d   e
| G | * | g |
  a   b   c 


Algebraic. Anything happening in ordinary space is preceded by a 1, anything happening in hyperspace is preceded by a 2.

In this notation, ordinary space looks like this:

1a1 1b1 1c1 1d1 1e1
1a2 1b2 1c2 1d2 1e2
1a3 1b3 1c3 1d3 1e3
1a4 1b4 1c4 1d4 1e4
1a5 1b5 1c5 1d5 1e5
1a6 1b6 1c6 1d6 1e6
1a7 1b7 1c7 1d7 1e7
1a8 1b8 1c8 1d8 1e8
and hyperspace looks like this
2a 2b 2c

Rules About Pieces

The Star Cluster (C): May move without capturing either one square forward or one square diagonally backward; Star Clusters may capture by moving either one square backward or one square diagonally forward. Star Clusters are unaffected by Black Holes and may move on and off of them, they may not, however, use them for any form of teleportation.

The Planet (P): Moves and captures like a Knight in standard chess. If a planet moves onto a Black Hole it is obliterated by strong gravitational fields and removed from the board. If the Black Hole in hyperspace is occupied, this does not happen, but upon being unoccupied, all Planets on Black Holes are removed from the board.

The Spaceship (S): Moves, but does not capture, by by going up to two spaces orthogonally. Spaceships may not go through other pieces. Spaceships capture, but not by displacement: They have high tech guns with which they shoot at any piece that lies along an unobstructed diagonal from them, such a capture constitutes a turn. Special rules apply to Spaceships and Black Holes which shall be discussed later on.

The Galaxy (G): Moves like a King in Standard Chess. A Galaxy may not be captured. The only piece that a Galaxy can capture is a Nebula, which is captured by the move of a Chess King. Special rules apply to Galaxies and Black Holes which shall be discussed later on.

The Nebula (N): Moves and captures like a Rook in Standard Chess but it may not cross any square which is in any another pieces capture zone (the set of squares on which a piece could potentially capture another, were it to be there), including one belonging to the owner of the Nebula and that of the opposing Nebula. The Nebula may, however, land on such a square. Similar rules apply for Nebulae and Black Holes as those which apply for Star Clusters. Nebulae may not move twice in a row. If a player is forced to move his Nebula in two consecutive turns, he must pass on the second. He can move on the turn immediately following his pass, and this is the only circumstance under which a player may pass.

Capture of one's own pieces is permissible

Special Rules Pertaining To Hyperspace

Only Galaxies and Spaceships are permitted to go into hyperspace. No piece may remain in hyperspace for more than five consecutive turns unless it is impossible for them to leave (if the Black Hole in hyperspace is blocked by another piece on the fourth turn, or if all of the possible exiting moves are blocked by other pieces by the fifth turn). If such a move is blocked, a piece must exit hyperspace on the next move on which it is possible to do so. If this implies moving to the Black Hole, a piece must do this first, even if all of the Black Holes in ordinary space are occupied. While in hyperspace all pieces retain their ordinary moves. There are no compulsory moves in ordinary space, but a move in ordinary space is postponed by necessary maneuvering in hyperspace. No piece may be taken while in hyperspace (for obvious reasons: neither of the pieces that can go to hyperspace can take each other with legal moves within the board).

Black Holes

Any Planet that moves onto a Black Hole is removed from the board. If the Black Hole in hyperspace is occupied, the Planets are immune to this effect. Upon removing the piece from this Black Hole, however, all planets on Black Holes are removed from the board.

Star Clusters and Nebulae interact with Black Holes as they do with ordinary squares.

Any Spaceship that moves onto or over a Black Hole in ordinary space is automatically transported to the Black Hole in hyperspace. If the Spaceship has only moved the first of two squares in ordinary space, and the appropriate square in hyperspace exists and is unoccupied, the Spaceship may move to such a square.

Any Spaceship that is on the Black Hole in hyperspace may move to any unoccupied black hole in ordinary space, and make a mandatory displacement of one or two orthogonal squares such that it is not on a Black Hole (ie: No Spaceship may end a turn on a black hole in ordinary space).

If the Black Hole in hyperspace is occupied, a Spaceship in ordinary space may not move onto or over any Black Hole in ordinary space. This rule does not affect shooting captures.

Any Galaxy that is on a Black Hole, may warp to any other unoccupied Black Hole, this move constitutes a turn. There is no mandatory, nor optional rule to permit Galaxies to move before or after they have warped on the same turn.

The End Of The Game

The object of Outer Space Chess is to capture the opponent's Nebula. If a player does so, this player is the winner. This capture may only be made by the Galaxy (no need to worry, it is embedded in the rules).

A player may also win if his opponent resigns.

A draw is reached via stalemate, or if both players have moved 30 times without taking any pieces (30 may sound awfully high, but looking at some of the possible endgame combinations it actually seems quite reasonable).

A draw may also be reached upon agreement.


The strategy and tactics section only discusses the "standard" variant described above. Let it also be noted that this is the only variant that enters the competition.

Variants are not described specifically, but listed in classes, from which several different sets of rules might be applied.

  • Variant A: The most obvious of them, change the size and shape of hyperspace, possibly adding a couple of Black Holes. I believe the three square hyperspace to be ideal (the reasons become clear when discussing strategy), but others may not think so.

  • Variant B: Black Holes are placed randomly on the boards, as opposed to in fixed locations.

  • Variant C: Reverse the roles of the Galaxies and Nebulae (this was the original idea, but it proved to be FAR more interesting to have them work as they do now). Certain rule modifications concerning hyperspace have to be implemented to keep Galaxies from hiding in it. Several are possible.

  • Variant D: Replace Planets and/or Star Clusters with other pieces. A good number of possibilities exist, but few of them seem to fit the game nearly as well as their conventional form.

  • Variant E: Replace Nebulae and/or Spaceships and/or Galaxies with other pieces. These variations constitute drastic changes in the game, and are much less along the lines of the intended form than the present version.

  • Variant F: Remove the Galaxy-Nebula system and make it possible to take all pieces and check and mate the Nebula (or the Galaxy, it really doesn't matter). This variant is really sort of cheating and I don't like the idea much, it's trying to make a game work more like Chess, even when it really wasn't designed for this sort of game ending.

  • Variant G: Remove or change the restrictions on Nebula Rook movement. Also consider expanding it to the full movement of a Queen in Orthodox Chess, with slightly stronger restrictions. This variant is encouraged. The specified system of movement for the Nebula was arrived at mostly arbitrarily, after a bit of trial and error with other forms. It will probably be hard to make a more interesting royal piece than the Nebula, but minor tweaking should probably keep things just as interesting, and might lead to beneficial results.

  • Variant H: Different board shapes and sizes.

Strategy And Tactics

Not actually having played this game, some of this might be wrong, but I'll try to provide at least some of the reasoning behind it.

The Spaceship is by far the most powerful piece. It's ability to take without moving makes it extremely difficult to counter, as there is no way to directly defend a piece from the attack of the Spaceship. Although the values of all of the pieces in this game (with the possible exceptions of Star Clusters) are hard to measure objectively, the Spaceship certainly stands well above any of the other pieces, and should be handled with care. The only real problem with Spaceships is that they tend to get stuck in hyperspace just when they are most needed.

After the Spaceship, the other pieces are much closer together. The next piece is probably the Nebula, as strange as it might seem for a royal piece to be among the most powerful. I admit to having designed the Nebula to make it the most interesting royal piece I could possibly come up with. It is more mobile than any other piece, including the Spaceship, and is not barred from taking pieces, as the Galaxy is. Direct defense against capture by a Nebula is ineffective, and since no piece captures orthogonally, except for the Galaxy (which is special), the Nebula (also special) and the Star Cluster (which can only do so in one of the four orthogonal directions) there is no piece that can defend itself from capture.

The Planet comes next, as it is just about as powerful as the orthodox Knight, even though it is barred from some squares most of the time. It is the only piece that can jump (except for Galaxies, which can effectively jump from Black Hole to Black hole). The real problem with the Planet, is that many of the more useful positions for it to occupy are all taken up by Black Holes, so it may not be as powerful as it seems.

The Star Cluster is actually far more powerful than the orthodox Pawn, and shouldn't be underestimated just because there are so many of them. Although Star Clusters do not promote, they are probably the most flexible pieces in the game, not being forced to do anything weird because of Black Holes, nor designated exclusively for interaction with the ever present Galaxy-Nebula duo. this piece is about even with the Planet, I can't quite tell which is more powerful.

The Galaxy is last. Although this piece is essential to win the game, it is extremely easy to trap it in hyperspace and block it off. It is also of extremely limited offensive value, as there is only one piece on the board that it can take. As a defensive piece, it is great, because it is immune to all capture. This is a good piece to try to use to neutralize the Spaceship, not only by blocking diagonal captures and two square motion, but also for stuffing it in hyperspace and not letting it out. Its ability to move freely through Black Holes makes it almost as mobile as the Nebula, which in this game, is saying a lot.

There are a couple of strategies that can be used to force a draw, but I am not going to discuss them, because they all require having superior force to that of the opposing player, and in that case, its a better idea to go for the win instead.

Taking the Nebula might seem like an impossible task. How is it possible to mate a piece that moves like a Rook? Especially when there is only one piece that can do it, and this piece can only move like a King? In fact, this is not nearly as hard as it sounds. Depending on several factors, it may even be easier than checkmate in Orthodox Chess. For one, the restrictions on the Nebula's movement through a square under attack greatly reduces the mobility of the piece, if the attacker plays correctly. The rule against moving it on successive turns also slows it up a great deal. The fact that another Nebula might also be the piece that interferes with movement automatically implies a variant of the Xiang Qi/Congo sort of "line of sight" rule. Note that on an empty board, if a Galaxy and a Nebula are placed in any position, the Galaxy can capture the Nebula. This leads to the possibility of non-drawn games where both sides have only a Galaxy and a Nebula. There are certain positions in which one player can win; hence the 30 move rule: There is no such thing as a draw by lack of force.

If pointers is what you want, try to block a Nebula's lines of motion. Remember that not only your own pieces block your opponent's Nebula, but also his own. One of the primary reasons I incorporated the rule that permits you to take your own pieces is to enhance the defensive potential of the Nebula that is hopelessly surrounded by its own pieces. It may also be useful to suicide your Planets by moving them onto Black Holes, thus freeing your Nebula from tight situations.

The more pieces are on the board, the more difficult it is for a Nebula to move. Attacks early in the game are more effective than you would think.

It is also important to note that unlike Orthodox Chess, a player never concludes a game by being perpetually on the attack. Since a Galaxy cannot be taken, it is always possible to lose inadvertently by having a your opponent's Galaxy sneak away your Nebula.

Of primary importance to the game is the issue of Black Holes and hyperspace. A perpetual battle will occur between your Spaceship and Galaxy and those of your opponent for control of what goes on in here. The fact that the two Galaxies start out in hyperspace leads to the possibility of immediate mayhem right from the beginning. Before I discuss this in detail, it might be a good idea to restate the rule for moving out of hyperspace, as I realize that it is slightly ambiguous.

No piece may remain in hyperspace for more than five turns unless it is impossible for it to avoid remaining there: To define this impossibility we will use the following criteria:

  • If a piece is not on the Black Hole's square, but is in hyperspace, and three or more moves have passed the next move of the player must be to move his piece onto the Black Hole, so long as the Black Hole square is not occupied.

  • If a piece has been in hyperspace for four moves or more, and is now on the Black Hole square in hyperspace, the next move of the player after the piece has entered hyperspace must be to move it to back to ordinary space, so long as a legal move exists that will let him do so.

  • If a piece has not made one of the above moves because it was not legal (ie: the Black Hole was occupied, or there was no legal move that permitted the piece to go back to regular space) the piece must make such a move as soon as it is legal.

I may well have not even implemented this rule if it hadn't been for the possibility of forcing a draw by trapping the opponent's Galaxy in hyperspace indefinitely by placing a piece on the Black Hole located in hyperspace. Further inspection reveals that this rule is far more interesting than I had originally planned.

Trapping pieces in hyperspace and not letting them out is an essential strategy. A Galaxy is a necessary piece to win the game, and the Spaceship is the single most powerful piece in it. You might think a good strategy would be to keep the Spaceships away from the Black Holes, but there are enough of them, strategically placed, that such a move drastically reduces the Spaceship's mobility. The same could be thought about a Galaxy, but the Galaxy, for one, must at least start in hyperspace, and placing it in hyperspace might be a good idea in order to try and block Spaceships. You might also think that there is no reason to ever move to any square in hyperspace other than the Black Hole square, but this keeps the Spaceships from entering hyperspace (impossible to trap them in it if they don't enter) and it also lets the Planets roam freely. Both of these situations are often inadvisable. It is possible to have all pieces but one of the two Spaceships and Galaxies trapped in hyperspace if you can control the square with the Black Hole on it. This will permit you to wreck havoc on the board with your remaining piece. Pieces that have been in hyperspace for a while are forced to leave. This is a good way to buy moves with which to screw around in ordinary space while your opponent watches helplessly. Given the power of the Star Clusters, it is not as hard as it sounds to occupy all of the black holes in ordinary space. If you can do this while your opponent's Galaxy is in hyperspace, you are guaranteed victory, no matter what. The real problem is that it is hard to keep your pieces there if your opponent is serious about forcing them off.

Thus ends the explanation and discussion of Outer Space Chess

Written by Nicholas Kuschinski.
WWW page created: April 7th, 2003.