Phase Chess -- Intro and General Rules
While experimenting with possible scenarios of 4-dimensional tic-tac-toe, my mind made a big phase shift into (what promises to be) a nifty four person chess variation. Here's the low-down as it occurred to me, and a few thoughts on it after playing one game, and the complete rules, and some variations.
I kicked around several names for this, mostly centered around the idea that you're playing twice at once. But, I think my friend Dave was right.... in saying... 'Phase Chess'. After playing for even a few moves, you'll see how your partner's pieces phase in and out of your play.
This requires four players and four boards (w/full chess pieces on each). [Actually, if you're really together, you only need two sets of pieces, but I highly recommend four sets of pieces (and if you're really slick you may want 8 sets of pieces if you can distinguish sets, but that's for you to decide).]
The players sit in a square. Opposite players both play the same color and are both playing against adjacent players. For example (after 1. e4 ... Nc3 ... ):
Players one and three start. Each player must make the same move in both games he/she's playing. If a move isn't legal in one of your games, it isn't legal. An example opening would be...
player1 player2 player3 player4 1. e4 e5 Nc3 Nc6
The three immediately obvious variations center around what to do with dead pieces.
Big note: It's easy to be in checkmate based on both games, but not on either on its own. The really tricky scene is when it looks like you're in check, but your partners pieces are blocking your opponent from fully attacking. We had one wicked setup with a stand-off involving three knights and two queens. One knight on one of my opponents boards was blocking me from taking my other opponent's queen. The positioning of one of my partner's knights was preventing the other queen from taking mine, and even if it had, it would have been a trade of pieces because I had a knight guarding my queen. I suppose you'd have to see it. But, you'll get the basic point in under a half-hour.
Caveats When We Played
First off, we chose version 'a', for simplicity (or so we thought). My partner and I got into all sorts of situations where we made the mistake of having him kill a piece that was going to protect my move. When the piece disappeared from one of my boards, we both ended up hosed. Our opponents fell into this once, but we almost missed it and ended up with an odd number of dead pieces (a "dead" giveaway).
Pawns were almost worthless. They couldn't attack, unless they could attack in both games (easy to avoid). They were more of a nuisance in that you could never realize your rooks until some of the pawns were out of commission.
Teamwork was of utmost importance. The person opposite you greatly affects your games. This isn't a problem. This, in fact, is the one of the major highlights of the game. But, we hadn't decided on timing issues before we got underway. We got into several situations where, if I moved, and then my partner moved, we'd both take a piece. But, if he moved, then I moved, only one of us would take a piece.
After we noticed this problem, we decided that both black moves should happen simultaneously, and both white moves should happen simultaneously.
The problem that then arose, was: could you move into check at the same time your partner was blocking that check for you? We eventually, ditched sheer simultaneous play into, if it didn't matter whether you or your partner went first (in terms of points and check), then you could play it in either order. I don't think that's going to be the proper way for two reasons: 1) it's hard to sort all of that out, and 2) order would still affect the final board position.
player1 player2 player3 player4 1. N-b7+ Rxh6 -- vs. -- 1. Nxh6 Rxh8++
So, it's clear that the 'order' rule becomes a very key element of this game.
Suggestions for better play
Make pawns be able to attack diagonally even if it's only taking in one of the boards. (If this makes them too powerful, then maybe make it a suicide attack -- it takes but dies??).
Fix ordering question by:
It may also be interesting to play blind (in which you don't get to see any boards but the two you're playing on). Or to play mute, open eyes, no cross-talk.
I'm interested in playing the 6-person/9-board/3-game-at-time scenario, but I'm not sure that I'll ever get that much interest, equipment, and time together.
We played for four and a half hours last night before we bailed in favor of playing some other time with a pre-defined order rule and something better for pawns.
Note on the 4-D tic-tac-toe.... we've been playing on a 4x4 grid of 4x4 boards. We're not sure yet if we're going to have to go to 6x6 of 6x6. But, we're pretty sure that 4-in-a-row, is a good enough ending goal for any number of dimensions. Actually, as I think about it, it may be possible to work stuff into a circular pattern in enough space. And, I think it would be most excellent to play infinite-dimensional tic-tac-toe... (adding dimensions as needed). It wouldn't have much advantage over its 50-dimensional siblings, outside of novelty. Here's some infinite dimensional tic-tac-toe for those of you with python: source.