1D Chess
by burnt-resistor on 4/10/2026, 3:37:28 PM
https://rowan441.github.io/1dchess/chess.html
Comments
by: hackyhacky
If you enjoyed this, you might like Mind Chess, which can be played without a board and pieces [1]:<p>Consider Mind Chess. Two players face each other. One says "Check." The other says "Check." The first says "Check." This continues until one of them says, instead, "Checkmate." That player wins -- superficially. In fact, the challenge is to put off checkmate for as long as possible, while still winning. This may be better stated: you truly win Mind Chess if you call "Checkmate" just before your opponent was about to.<p>[1] <a href="http://www.eblong.com/zarf/essays/mindgame.html" rel="nofollow">http://www.eblong.com/zarf/essays/mindgame.html</a>
4/10/2026, 6:00:36 PM
by: quuxplusone
Mentioned in TFA: This version of chess is given by Martin Gardner in his "Mathematical Games" column of July 1980 (pages 27 and 31) — <a href="https://www.jstor.org/stable/24966361" rel="nofollow">https://www.jstor.org/stable/24966361</a> — and the analysis of White's mate is given in the column of August 1980 (page 18) — <a href="https://www.jstor.org/stable/24966383" rel="nofollow">https://www.jstor.org/stable/24966383</a>.<p>I do wonder how things would change if the board were 9 cells long; 10 cells long; etc. Also, it seems "in the spirit" to permit castling if neither K nor R has moved yet: i.e., from the position<p>K _ R N r _ n k<p>White ought to be permitted to<p>_ R K N r _ n k<p>(Or maybe there's a stronger argument for R K _ N r _ n k, actually. The former was conceptually "rook moves halfway toward king, then king moves to the other side of rook"; but the latter is "rook moves two steps in king's direction while king moves to the other side of rook.")<p>I'm pretty sure this wouldn't change the analysis on the 8-cell board at all, though. I wonder if it would change the analysis on any size of board.
4/10/2026, 4:45:32 PM
by: aktenlage
Very cool. Reminds me of 1D Pacman: <a href="https://abagames.itch.io/paku-paku" rel="nofollow">https://abagames.itch.io/paku-paku</a>
4/10/2026, 6:24:02 PM
by: tromp
1D Go is also interesting and doesn't require any change in rules or starting position. TIL that it is known as Alak [1]. One of the open problems in our Combinatorics of Go paper [2] is whether you can play a game that goes through all possible legal 1xn positions for any n>2, which we were only able to verify up to n=7.<p>[1] <a href="https://senseis.xmp.net/?Alak" rel="nofollow">https://senseis.xmp.net/?Alak</a><p>[2] <a href="https://tromp.github.io/go/gostate.pdf" rel="nofollow">https://tromp.github.io/go/gostate.pdf</a>
4/10/2026, 7:24:00 PM
by: asibahi
This is really nice.<p>Incidentally, there is an actual 1D game that is one of the most popular games on the planet: Backgammon.
4/10/2026, 4:18:12 PM
by: freetime2
I tried and failed a couple times before looking at the hint. And then I had to ask ChatGPT to explain the hint because I didn't understand chess notation. But with all of that out of the way, I am now winning 100% of my matches and feel it's not an overstatement to call myself a 1D chess grandmaster.
4/10/2026, 9:39:51 PM
by: gef
Reminds me of Edwin A. Abbott's Flatland, where he describes Lineland. A one-dimensional world whose King can only move forward and backward, cannot conceive of sideways, and considers his tiny segment of existence complete and sufficient. The Linelanders are portrayed as pitiable, intellectually imprisoned by their single dimension. Much like us in our three :)
4/10/2026, 4:51:35 PM
by: chedoku
If you like 1D chess, you'll probably like other chess-themed puzzles as well: <a href="https://chedoku.com/blog/chessPuzzles" rel="nofollow">https://chedoku.com/blog/chessPuzzles</a>
4/10/2026, 7:17:13 PM
by: yuppiepuppie
This is my kind of chess :) I’ve added it to the HN Arcade <a href="https://hnarcade.com/games/games/1d-chess" rel="nofollow">https://hnarcade.com/games/games/1d-chess</a>
4/11/2026, 6:34:12 AM
by: northfield27
Haha, i was taking N4 and N6, but didn’t figure the steps after that.<p>To win we need to let knight die because rook can move multiple steps to kill the king.<p>From a third person perspective R2 is a deceptive move that takes advantage algorithm to make the black king back off to kill its knight.
4/10/2026, 4:40:09 PM
by: juleiie
That finally confirmed that I am too regarded for chess if even 1D is too hard yay
4/10/2026, 5:33:38 PM
by: sieste
It took me an embarrassing number of attempts to win.
4/10/2026, 4:19:47 PM
by: MinimalAction
I love chess! This version was fun too.<p>If 1. Rx6,it is stalemate. So it must be 1. N4 N5. Then we could proceed with, 2. Nx6+ K7. Now, if you capture the knight (Rxe), it is stalemate again. So sacrifice the knight, 3. R4 Kx6 so that you force black to zugzwang with 4. K2 K7, and finally, 5. Rx5#
4/10/2026, 8:03:16 PM
by: bdcs
Trying to lose is also fun (as white)<p>Some observations:<p>* Knights are color bound<p>* You can mate with Knight & King (K+K is still insufficient material)<p>* 3 fold repetition still applies (and has a popup!)
4/11/2026, 12:36:15 AM
by: deadlypointer
Even in the winning line black can force stalemate in multiple ways,how is it a forced win?
4/11/2026, 6:14:03 AM
by: ergocoder
There aren't that many combinations. I finally won hahaha
4/11/2026, 4:00:04 AM
by: schmeichel
Finally, a version of Chess I can understand. Thank you.
4/10/2026, 4:15:11 PM
by: mcdeltat
Ok seems like I don't understand and really dislike chess stalemate/draw rules. So if I make a move which is directly causative to my opponent having no moves which would not result in checkmate, this means the same is a draw?? That makes no sense to me.
4/11/2026, 1:21:28 AM
by: topce
I went in other direction ;-) <a href="https://topce.github.io/chess960x32/" rel="nofollow">https://topce.github.io/chess960x32/</a>
4/10/2026, 6:57:14 PM
by: palata
It was a lot more fun than I first thought!
4/10/2026, 4:42:45 PM
by: anotheryou
Is this stalemate correct? <a href="https://imgur.com/a/Z7in8sl" rel="nofollow">https://imgur.com/a/Z7in8sl</a><p>Have not even lost a piece yet!
4/11/2026, 1:04:22 AM
by: daynthelife
It frustrates me that the site does not give the strongest defense for black. The position is mate in 6, not 5:<p>1. N4 N5<p>2. Nx6+ K7<p>3. R4 N3+!<p>4. K2 N5<p>5. N8! Kx8<p>6. Rx5#
4/11/2026, 12:19:35 AM
by: igor47
Oh I made one of these once! In mine you play against other people. <a href="https://1dchess.igor47.com/" rel="nofollow">https://1dchess.igor47.com/</a>
4/10/2026, 11:41:53 PM
by: frunkp
Those who play go may enjoy the variants: <a href="https://www.govariants.com/variants/rules-list" rel="nofollow">https://www.govariants.com/variants/rules-list</a> Tetris is a fun one to try!
4/10/2026, 8:10:29 PM
by: hart_russell
I don’t know why this is stalemate: N4 N5, N6 K7, R5. Wouldn’t rook have the king in checkmate?
4/10/2026, 5:56:24 PM
by: kkaske
I was only able to beat this after a couple retries. The hint was hard to read.
4/10/2026, 4:49:23 PM
by: hypendev
Don't know when was the last time I had so much fun with chess. Quite intuitive, clicked on the first click.<p>Would enjoy so much if there were more of these, feels like an obligation-free chess puzzle.
4/10/2026, 6:13:49 PM
by:
4/10/2026, 4:52:23 PM
by: dwa3592
I am ashamed to admit that i could not solve that even though i consider myself a decent player.
4/10/2026, 8:33:41 PM
by: bbx
Oh very interesting. Even with these restrictions, there are quite a few variations, and it seems only one ends up with white winning.
4/10/2026, 4:25:43 PM
by: darepublic
I won after four attempts. Pretty sure it was perfect play so yes white has forced win
4/10/2026, 5:55:25 PM
by: armanhq
More fun than I expected! Thank you :)
4/11/2026, 12:15:48 AM
by: sjdv1982
Zugzwang!
4/10/2026, 6:01:47 PM
by: phplovesong
Basically tictactoe. Ends in a draw every time.
4/11/2026, 5:55:07 AM
by: hybirdss
spent way too long on this before realizing the knight is basically the whole game in 1d
4/10/2026, 11:50:41 PM
by: gcheong
Minor typo: assming -> assuming :)
4/10/2026, 8:29:24 PM
by: tempestn
That's actually a fun little puzzle.
4/10/2026, 5:52:50 PM
by: keeganpoppen
that took me way longer than i thought it would, but made me all the happier for it
4/10/2026, 8:42:50 PM
by: lschueller
Cool idea. This is smart and lean. I like it
4/10/2026, 4:32:44 PM
by: mememememememo
Nice little puzzle!
4/10/2026, 11:22:48 PM
by: rOOmbambar9
It's very interesting and fun!)
4/10/2026, 5:03:02 PM
by: Dante77711
Nice, fun and interesting! :)
4/10/2026, 7:07:15 PM
by: addybojangles
Silly nice brain teaser
4/10/2026, 5:39:04 PM
by:
4/10/2026, 5:04:05 PM
by: MagicMoonlight
Why does it end in a stalemate if all my pieces are alive and they have none? That’s not a stalemate, I can move freely and get them.
4/10/2026, 8:20:01 PM
by: jibal
N4 N5 Nx6+ K7 R4 Kx6 R2 (or K2) K7 Rx5#
4/10/2026, 8:17:59 PM
by: slopinthebag
I was confused why 3.R2 is drawing, but not 3.R4 since black can check with the knight either way, but it's fairly obvious in hindsight - if black checks instead of capturing, you don't take, you go K2 and force black into zugzwang. Clever.
4/10/2026, 8:08:19 PM
by: abhinaystha
creative!!!
4/11/2026, 12:41:51 AM
by: tkapin
Nice! :)
4/10/2026, 4:10:53 PM
by: chatmasta
Wow, Trump’s job is harder than I thought.
4/10/2026, 10:50:40 PM
by: naorz
Fun stuff, love it!
4/10/2026, 3:52:10 PM
by: Computer0
I was expecting a blog post regarding Iran strategy...
4/10/2026, 7:32:19 PM
by: hfnjdbekwbiw
Hello
4/10/2026, 7:13:10 PM
by: Keyframe
This is stupid. I like it!
4/10/2026, 8:29:48 PM
by: sillyfluke
I honestly thought this post was going to be about the Iran war.
4/10/2026, 8:17:26 PM
by: Nevermark
I thought for sure this article was going to be political commentary!<p>(I would pay a lot for some fat 1500 page, leather-bound tome of wisdom and anecdotes about historical foot guns, by Carl von Clausewitz, titled "1D Chess". And it's inevitable multi-authored, Harvard-published much thicker contemporary-world sequel.)
4/10/2026, 8:50:14 PM
by: cindyllm
[dead]
4/10/2026, 9:05:04 PM
by: frostyel
[dead]
4/11/2026, 6:16:52 AM
by: hfnjdbekwbiw
[flagged]
4/10/2026, 7:13:35 PM
by: BiraIgnacio
love it!
4/10/2026, 5:48:55 PM
by: vladde
i could not beat it, and i can't read that chess notation
4/10/2026, 4:37:30 PM
by: tintor
The first move is always: white rook takes black rook, then the only remaining move for black is to move the knight away, which results in checkmate.
4/10/2026, 4:36:19 PM