The main reason for that is time traveling and dimension hoping come at a tempo disadvantage. When you create a new timeline, you make 1 move, but give your opponent 2 moves. You used your turn in the present, and created a new board where it's their turn in the past.
Any time travel or dimension hops need to be worth twice as much, minimum, as a normal move to even consider making them.
It does have more depth than normal chess, but it's not infinity deep. I still love it. My biggest concern with high level chess matches is that many, many games end in draws. It feels like it's impossible to a draw a gam e in 5D chess' 
I.e. you only have the tempo disadvantage once the present has caught up to where you traveled from
Doesn't it depend on the piece you use? Knights and Bishops seems to be able to move on the board and move back in time at the same time.
If you add probabilistic moves, the optimal way to play would be to give each alternative move the same weight (ie probability) that you think it will win you the game. You would pull this probability out of your mental representation.
Something like, "I think this is the best move, but this one is really good too so I will do it as well".
So I guess it could be fun to be able to try out all the moves you think are good in this way. But then an easier way to achieve this is to just play the game normally and go back to an interesting previous position once you have won.
But maybe a set of rules that will allow you to still win the game 'in retrospect' after all the 'best' moves were played by going through all the alternative superpositions as well.
So basically just play normally, but when you doubt what move is best, you make a superposition (and assign probabilities), which means you will be going back to this position later.
The winner would be the one who won most often, with each win weighed by the probability of that outcome (calculated based on the assigned probabilities along the game).
Sounds like fun.
for extra fun if one board gets to a position that another board already had, the tree could be merged again.
The game starts with each player having 50 points "in the bank". In addition to moving normally, players may opt to move and split the timeline. If they split, they choose how many points to dedicate to the new timeline, which are put in its bank, distributed evenly between both players. Points must be whole numbers and each timeline must have at least 2 (max 50 timelines). Play continues normally on the original timeline, and they may opt to split again, if they have the points.
When a given timeline is played to checkmate, the winner secures all of their own and their opponent's points from that timeline. In the case of a tie, points are split evenly. First person to secure over 50 points wins.
The game keeps track of the history in each timeline. If one timeline's board enters a state that already occurred in a different board's history, both players are asked whether they'd like to merge timelines, in which case the banks from each timeline are combined and play continues on the board that is farther in the future.
The UI allows players to switch which timeline they are looking at freely So, both players can be playing at once, in different timelines. Initial implementation can show a single board at a time, a number showing which timeline you're viewing, how many points each player has banked in that timeline, and arrows for moving between timelines. Should be pretty easy to add, actually.
Competitive variant is timed. There is a single clock for each player, which counts down by the sum of all timelines in which it is their turn, scaled down by the % of total remaining points in that timeline.
That is, say we're playing 10+10 and there are currently two timelines, one with 20 points and one with 80. It's my turn in the 80 point timeline and yours in the 20 point timeline. While we wait here, my clock ticks down by .8 seconds per second, and yours by .2. Then I play. I gain +8 seconds, and my timer stops while yours starts ticking at full speed.
You'll note this isn't quite the original idea; a faithful implementation of that would have a shared pot of points that each player can split arbitrarily (including fractions of a point). But I didn't want to allow infinite splitting because that would make the game unplayably long (or, in timed variants, might lead to optimal strategies of overwhelming your opponent with many splits). And if infinite splitting is not allowed, then I don't want to allow one player to do all the splitting, that's no fun for the opponent.
The one thing I don't like is that this allows the stronger player to reliably win by never splitting and just winning the original board, since it will always have >50 points. This is probably fixable, not going to spend more time thinking about it right now though; this post has taken long enough :)
You have to think several turns ahead, in a chess sort of way. But your "best" move may be a low probability move, so you have to weigh that. Same for thinking about what your opponent may do in return.
There exists some optimal play for both white and black, we don't know what it is yet, but someday we might and then chess would be truly solved like tic tac toe.
Btw, for anyone who likes time travel paradoxes, do watch Dark. It's up there
with Primer, but does your head in more because of how many characters there
So is this basically visualizing the tree of possibilities from any board configuration, overlaid on itself at nodes where different sequences of moves can result in the same board configuration, allowing you to "jump" to a different "timeline" through the 5th dimension?
If it were just presented as a fun exploration of what 10 dimensions could be, for fictional purposes, it would be... OKish, I guess. But choosing "10" specifically makes people erroneously think that this is what string theory is about, which is completely wrong.
Additionally, it falls into the trap of assuming that curvature requires a higher dimension to curve in, and that nontrivial connectivity inherently requires such curvature, both of which are false and hard enough to explain to people who have not been explicitly taught wrongly already.
And on top of all of that, it perpetuates the faulty idea that "the" 5th dimension, or "the" 10th dimension are sensible concepts, by presenting its particular choice of dimensions to discuss and its particular choice of ordering of those dimensions as fact.
Normal chess is 2 dimensions, plus you have time dimension (3D), plus you have parallel timelines - that always go just one dimension
So it's 4D and not 5D?
edit: yeah it's actually "just" 4D, from the explainer here
I have no idea what high-level play will end up looking like, but the streamer from whom I learned the above  said that the most common way to win is to mate a king on a board in the past. Those already have their options of escaping an attack restricted by ordinary chess rules; it gets worse when you can make additional threats from the future.
Yes. ( https://news.ycombinator.com/item?id=24065059 )
> You couldn’t do all timelines.
How do you reckon that? I mean, it makes sense on an intuitive level; however, since now we're not talking about Conor Petersen's 5D chess, but the vast space of possible multiverse time travel chess variants, it's not obvious how one could prove this to be impossible in a somewhat rigorous way. For example, what if time-lines end when a king is mated (or wioll fore-when haven been mote ), but you only lose when you can't make a valid move in any time-line?
For example, if your king moves from its square and an enemy rook attacks its starting position (rooks can move any number of squares in any one direction), then it's mate unless you can take the rook. However, if in the intervening time, another piece lands on the same spot, then it will block subsequent rook checks through time on that square.
However, I would say that real chess is sort of "2.5" D by this definition rather than full 3D, since the turn number coordinate of every piece can only go up, not down.
: The game's formalism is slightly complicated by the fact that a piece could make a move of (x, y, t, L) -> (x, y, t - 1, L) which would count as moving one square in one dimension, but then the game's "system" automatically transforms that move into a (x, y, t - 1, L +/- N) move. (The choice of +/- depends on which player made the move. The value of N depends on how many other timelines there are at that t.) This happens because of the rule that the past cannot be changed, so altering the past requires branching the timeline.
Similar things also happen with a move of (x, y, t, L) -> (x, y, t, L2), because within a single turn there is a concept of whether the board has already had a move played on it or not. So if the board at L2 has already had a move played on it, this new move is instead transformed into (x, y, t, L3). So it counts as a move of (L2 - T) squares for the purpose of validity, but is actually a move of (L3 - T) squares.
I think you're right. Even if we classify classical Chess as 3D (2D board + a time axis for game states), time travel re-uses that same time dimension.
If you wanted to shift the complexity into ludicrous speed (this is inspired by archgoon's comment ), you could introduce another dimension by putting a classical chess board inside each square of the 4D board. The 4D move only succeeds if you win the game on the mini-board. Just, please, don't bring recursion into this, unless you're captain Kirk and absolutely need to nerd-snipe a rogue AI. (“They've gone to plaid!”)
There's another possibility I've hinted at by calling standard Chess ‘classical’. On second thought, let’s not go to Quantum Chess. 'Tis a silly place. (I tried to imagine what a Schrödinger's king would look like. I've seen things you people wouldn't believe. Queens checked en passant from the future. I watched knigths glitter in the parallel time-line near the Hadamard Gate. All those moments will be lost in time, like tears in rain. Time to resign.)
1. Horizontal within a board
2. Vertical within a board
3. Backwards and forwards along a timeline
4. Up and down across timelines
5. The timeline of how the game actually evolves, building out the tree. This is a bit of a stretch, since you can't move pieces through it in the same way as the other four.
For instance, if you have a stick you can push back and forth in a groove and count that as one dimension, if you push hard enough against an obstacle the stick might break and rotate out into the plane, but that's still only two degrees of freedom.
I suppose the actually intended analogy is that by riding a horse, the character is more evasive and can slip past another unit without being blocked. Also, I suppose that rooks must have wheels on, and a door that a king can only walk through in rare circumstances.
* Every square of a chessboard is itself a chessboard. This applies recursively. The top-level chessboard is named "Prime". All other chessboards are named according to the subdivision of Prime where they are located. So, the board located one level deep at F3 is called "Prime-F3". The board located two levels deep at A7 of Prime-F3 is called Prime-F3-A7.
* All infinite chessboards start in the standard board starting position.
* Black and white alternate making moves. Each move consists of moving a single piece within a single chessboard, following standard chess rules.
* The game is won when a player does not have a King located in Prime.
So far, this only introduces additional moves that can be made, which have no impact on the Prime board. Apart from being harder to force a draw, the subboards have no impact. Next up, adding rules to allow boards to influence the boards above/below them.
* If player X has a piece on board Z in location Y, then all pieces belonging to player X in board Z-Y may, in addition to their normal move, also move like the piece in board Z. For example, at the start of the game, white has a queen on Prime at location D1. Therefore, in board Prime-D1 may move like a queen, in addition to their normal movement.
* If player X does not have a King in board Z-Y, then their opponent may, as their move, move any piece from board Z-Y to board Z in location Y. For example, if Black has captured White's King on board Prime-D8, then Black may move any piece on Prime-D8 to the Prime board at location D8.
Now, there is an incentive to playing on the lower level boards. Play here goes much faster, by virtue of having more moves available. By investing time into the subboards, you can gain additional pieces on the main board. If a subboard is being used to funnel more pieces in, then it may be worth investing in a subsubboard, in order to pull a king in from the subsubboard to the subboard.
Lot of games you could spin up in this manner. I wonder if we are going to do that for all the board games with tried and old strategies. HN has any suggestions on what those board games should be?
Game on steam: https://store.steampowered.com/app/1349230/5D_Chess_With_Mul...
There is a discord linked in the game help menu where people are discussing lot of things including how to create a bot.
For the lazy: https://discord.gg/8kQhp6
Edit: removed mobile url.
I was crazy enough as a high-schooler to actually build (with the help of my father) a 3D chess "board". It was mostly plywood, with eight 8x8 boards stacked vertically. I had previously gotten a "3D" chess board which was just three 8x8 boards. They weren't making Star Trek tri-dimensional chess sets back then.
With the 8x8x8 3D board, movement rules for 2D chess have a "natural" expansion to 3D, with only a few corner cases. White player's non-pawn pieces start out on the bottom board, with the pawns on the next board up.
In practice, it was hard to visualize how the game was going in general. We were constantly standing up and crouching to see. Only one of my friends wanted to play, and he only lasted about half a game. :-(
With the failure to interest my friends, I had intended to write my own chess program to play it. I had started out with the 2D version, and was then intending to expand it later. The original was written in BASIC... and that did not go too well.
This is kind of the opposite. So it really competes with Fall Guys then...