8 ms·

Show HN: Chess Twist

29 points by frading 2y ago

I continue my experiment of transposing classic games onto an irregular grid. I've previously released variants of minesweeper and checkers. And now I'd like to share my variant of Chess. Chess can be a pretty punishing game, but I thought this was nevertheless a way to make it even more challenging by making it trickier to anticipate your opponent, even though both players still have the same information. From the playtests I've done, that challenge is pretty compelling. It also seems to be more fun at 2 people, where both players keep surprising one another.

gus_massa 2y ago
So in this version the bishops can change the color they can move on? The corners with 3 and 5 neighbour have a special mark. What does that mean? Can you share how the board is generated or it's part of the secret special sacuce? I think a blog post about the generation of the borard with a few nice graphics can get a lot of traction here.
- frading 2y ago
  > So in this version the bishops can change the color they can move on? It's more that black and white colors don't apply anymore in a grid like this. Since there will be places where more than 4 tiles can share a same corner, you need more than 2 colors. So here, colors are only used for cosmetic reason, to differentiate the tiles from one another. That said, I've tried to keep the essence of classic chess where I could. And it's totally possible on the sides of the board, where it's guarantied to always have 8 tiles touching a side with a full edge. So for those, I'm alternating white/black and positioning the king and queen on the expected colors. But as soon as there is a corner with more (or less) than 4 tiles, the color assignment needs to adapt and that trickles down to the rest of the board. So in most boards, I need 3 or 4 colors, and in some cases I need 5 (but maybe my algo could be improved to limit that number). > The corners with 3 and 5 neighbour have a special mark. What does that mean? The red marks (which I call red wall) highlight where only 3 tiles are connected. And the blue ones (which I call blue pivots) highlight where it's 5, or even 6. They each generate different strategies. For the red wall, each tile that is touching it has a missing diagonal. So it acts like a wall, especially for the bishop and queen, but also the pawn. This wall can be great for defense. Or for rooks, this can be great for attack, as you can target 2 parallel lines from there [1] For the blue pivots, you have the opposite, as you have more than 1 diagonal. So if you have a bishop, it can go in 2 directions from this corner. I invite you to try the tutorial that opens up when you load the demo, it has a couple steps which illustrate those. Or maybe you have gone through it, and it's not clear enough? I'd be very happy to hear any feedback on this. I have a feeling this info could be more obvious, and that may not be the case yet. And for the board generation, I'm completely open about it. It's actually inspired by a game called Townscaper, and the author generously shared how he made it. I'm merely running with it. I've just written this short explanation on r/proceduralgeneration [2], which I'm copying it here: ------- The game is built using Threejs, Vuejs, and Polygonjs (my own 3D engine based on threejs). You can see examples of scenes where this type of grid is created [3] and the core library is open source here [4] You can also see the code for the most important node, called quadrangulate [5] In short, it takes a bunch of triangles, and convert them to quads by grouping them in pairs. This conversion is straightforward when the triangles are neatly aligned and you process them in order, and the output would then be a very regular grid. But if you process them out of order, you will en up with isolated triangles that have no more neighbouring triangles. Those can't be converted to a quad. But if you subdivide the whole thing, you then get an irregular grid like the one above. ------- What I forgot to mention is that after the subdivision, you may also need to apply a smoothing, or squarification, where you iterate several times of the whole grid to transform the tiles from a rhombus to be more like squares. And you're absolutely right, I should do a blog post about it. It's a question that comes up very often as well, it could do with a central place. And I'd love to see more people using this system, as interesting mechanics emerge from it. [1] https://x.com/fradingue/status/1796892307523830068/photo/2 https://x.com/fradingue/status/1796892307523830068/photo/2 [2] https://www.reddit.com/r/proceduralgeneration/comments/1d5np8w/chess_twist_a_mindbending_chess_variant/ https://www.reddit.com/r/proceduralgeneration/comments/1d5np... [3] https://polygonjs.com/gui/irregular_quad_relaxation/edit https://polygonjs.com/gui/irregular_quad_relaxation/edit [4] https://github.com/polygonjs/polygonjs https://github.com/polygonjs/polygonjs [5] https://github.com/polygonjs/polygonjs/blob/master/src/engine/nodes/sop/Quadrangulate.ts https://github.com/polygonjs/polygonjs/blob/master/src/engin...
  - gus_massa 2y ago
    > I need 3 or 4 colors, and in some cases I need 5 4 should be enough https://en.wikipedia.org/wiki/Four_color_theorem https://en.wikipedia.org/wiki/Four_color_theorem, but the alternating color in the border may be a problem. It's an interesting variant for nerdsniping. I guess it's possible to find a 4 color version but it may need too much backtraking. --- > I invite you to try the tutorial that opens up when you load the demo I didn't notice. It's linked at the top. You may add another link at the bottom for people like me that skip the headers. I'll try later. --- About the new strategies, in human vs computer the knight forks are probably more OP than a bunch of blinkstackers with infinite APM. I'd trade a rock or even a queen for a knight just to give my brain some rest.
    - frading 2y ago
      Yes, someone else here mentioned the four color theorem, and that gave me a few ideas to improve that. For the demo, it actually opens up when you start the game. But it's possible to skip it, which is totally fair, I should have expected that. I'll make the button more obvious, you're absolutely right that it's too hidden at the moment. > knight forks are probably more OP than a bunch of blinkstackers with infinite APM There are too many words I don't understand here to infer your meaning. The knight forks I know are when a knight threatens the king and another piece, but it looks like you mean something else. It could be related to what I mentioned with multiple diagonals, although that does not affect knights. And OP is probably not original poster. And I don't know what bindstackers or APM are (maybe Actions Per Minute?). But it does look like you know more about chess than I do, so I'd love to absorb that knowledge.
      - gus_massa 2y ago
        > There are too many words I don't understand here to infer your meaning. Sorry, I watched too many videos of StarCraft 2. OP means Over Powered, i.e. an strategy that is imposible to beat. % years ago, Google made an AI bot to play StarCraft 2, and they made a demo against two proffesional players. The bot was "cheating" so the bot has vision of the whole map, and the bot could make as many "clicks with the mouse" as it wants (APM "action per minute"). The bot discovered an estrategy that was to create some robots with lasers "stalker" that can shoot from a distance, so many of them can atact the same unit. And use an upgrade "blinck" so they can teleport a short distance. So the bot could make all of them atack and pick the hurt units and teleport to the back so the heal while continue atacking. A human can only manage 5 or 10 of them together, and there is a high chance of forgeting to send one to the back. The bot used like 30 of them, atacking from different angles. There is a video with clips of the game. The most clear fight were the bot (in blue) use the trick is https://www.youtube.com/watch?v=6EQAsrfUIyo&t=510s https://www.youtube.com/watch?v=6EQAsrfUIyo&t=510s --- I tried the demo. The default player is too weak. It makes too many silly mistakes. The harder players is hard. I'll try again tomorrow. (The bishops that bounce against the walls when there is a corner with 3 squares in the border are weird. Also, bishops are too easy to block by "walls". I like knights better.)
tromp 2y ago
Making Go Twist is a bit more straightforward, since the rules work unchanged for any undirected graph. Such as this diamond lattice [1] in which inner points still have 4 neighbours. [1] https://en.wikipedia.org/wiki/Go_variants#/media/File:VirgilGriffith.jpg https://en.wikipedia.org/wiki/Go_variants#/media/File:Virgil...
- frading 2y ago
  Ah that's interesting, thank you. Especially as Go is the one I'm the most unsure about, mostly because I've rarely played it. I have a feeling that making a semi-decent bot is going to be extra difficult. Or at least I'll need a better intuition of what a good bot would do first.
paipa 2y ago
Very cool! Looking forward to playing it. I suggest to minimize visual clutter, because any new player's brain will be overloaded trying to figure out a board, and less is sometimes more. I'd remove the forward direction triangles where they can be unambiguously inferred from the baseline. A lower grain contrast wood texture might be a good idea too. You mentioned you sometimes use five tile colours but you can probably improve it: yes, the four colour theorem guarantees that :)
- frading 2y ago
  Yes, minimizing clutter was a priority, and still is. I've tried to avoid those arrows for a long time, but the pawn movements wasn't clear enough without them. And I agree it's not the optimal display. Displaying them on some tiles only is something I have not thought of. My first reaction is that it may feel harder to read, as tiles with an arrow may look like they would act differently than those without? We may induce the idea that it has a different purpose. So for now, I'd prefer a solution that would look the same on all tiles, I think that's much easier to parse. But then I should probably give this a try before rejecting it. You do have a good point regarding the wood texture, I've tried other textures, but couldn't find a better one yet. But I'm sure that's possible. Nevertheless for now, you can also display different skins: https://imgur.com/a/zitKlpz https://imgur.com/a/zitKlpz And thanks a lot for mentioning the four colour theorem. I'm looking at its wikipedia page now. I'm sure I came across it many times before, but I did not think about it when tackling this part of the problem. My implementation is here is anyone can spot my mistake: https://github.com/polygonjs/polygonjs/blob/master/src/engine/nodes/sop/QuadUniqueNeighbourId.ts https://github.com/polygonjs/polygonjs/blob/master/src/engin...
  - wizzwizz4 2y ago
    The five-colour theorem was first proven in the late 19th century. The known proof of the four-colour theorem is non-surveyable. There's probably no small mistake in your implementation, and the solution you should go with is unlikely to be a fully-general algorithm. (I'd suggest starting from the border on the outside, greedily filling in as many choices as are forced (up to isomorphism), then randomly choosing a candidate breadth-first or depth-first until you've found a four-colour solution.)
jncfhnb 2y ago
Pawns should probably have a piece that indicates their orientation. As far as I can tell it is impossible to discern which way a pawn moves without querying the ui.
- frading 2y ago
  There are those little black and white arrows on each tile, which indicate which way is forward for a specific player. Does that help? Or maybe you saw them and you mean something else? Interestingly, someone here mentioned that those arrows add a lot of clutter, and someone else on twitter said they only noticed them after I pointed them out. It's interesting how people perceive things like that so differently.
  - lucasmullens 2y ago
    It might be worth considering just changing the rules for the pawn to deal with this. It's hard to tell what it means to move "forward" on a board like this, even after understanding the indicators. Maybe pawns could just move horizontally/vertically and attack diagonally, regardless of color?
    - frading 2y ago
      That's an interesting suggestion. The pro is that it will simplify things, remove visual and cognitive clutter. The con is that we stray away from classic chess rules, which I'd still like to avoid as much as possible. I will think about it. It may be possible to allow as an option.
      - paipa 2y ago
        Your constraint should be that if the board is the special case of regular chess, the game should play exactly the same. Allowing the pawn to move towards any side is too much because it would violate this principle. Perhaps define forward as the direction(s) which, when extrapolated as a rook, would reach the opponent's backrank. If it doesn't exist, the direction(s) which, when extrapolated, terminate on the opponent's half. This would allow extra freedom to pawns in some funky topologies that can occur in your game, but generally follows the principle of least surprisal.
deleted 2y ago
[deleted]
SamBam 2y ago
This is very cool, I'm enjoying it. One small note: I tried to castle, and was told "Castling is not allowed because your king was previously in check." This isn't one of the rules of castling in regular chess. [1] Also, it would be nice to implement the three-same-position draw, since I got trapped in a cycle of just moving my king back and forth forever. 1. https://en.wikipedia.org/w/index.php?title=Castling#Requirements https://en.wikipedia.org/w/index.php?title=Castling#Requirem...
- frading 2y ago
  great to hear, thanks a lot! Thanks a lot for the correction regarding castling. I did look up this page a fair bit when implementing this, and I swear I had seen the rule that castling wasn't possible if the kind had been in check. But looks like I was dreaming. So I'll fix that shortly. For the three-same-position draw, yes, it's on my list. It was really low priority, but your comment makes me move this up the list. I had improved the bot so that it would be better during the end game, thinking that would avoid the need for this rule, but it looks like that doesn't work all the time (which shouldn't be surprising). So yes, I'll work on that as well, That's great feedback, thanks a ton.
- frading 2y ago
  I just fixed the castling bug. Thanks a lot for letting me know.

29 points by frading 2y ago

gus_massa 2y ago

So in this version the bishops can change the color they can move on? The corners with 3 and 5 neighbour have a special mark. What does that mean? Can you share how the board is generated or it's part of the secret special sacuce? I think a blog post about the generation of the borard with a few nice graphics can get a lot of traction here.

frading 2y ago
> So in this version the bishops can change the color they can move on? It's more that black and white colors don't apply anymore in a grid like this. Since there will be places where more than 4 tiles can share a same corner, you need more than 2 colors. So here, colors are only used for cosmetic reason, to differentiate the tiles from one another. That said, I've tried to keep the essence of classic chess where I could. And it's totally possible on the sides of the board, where it's guarantied to always have 8 tiles touching a side with a full edge. So for those, I'm alternating white/black and positioning the king and queen on the expected colors. But as soon as there is a corner with more (or less) than 4 tiles, the color assignment needs to adapt and that trickles down to the rest of the board. So in most boards, I need 3 or 4 colors, and in some cases I need 5 (but maybe my algo could be improved to limit that number). > The corners with 3 and 5 neighbour have a special mark. What does that mean? The red marks (which I call red wall) highlight where only 3 tiles are connected. And the blue ones (which I call blue pivots) highlight where it's 5, or even 6. They each generate different strategies. For the red wall, each tile that is touching it has a missing diagonal. So it acts like a wall, especially for the bishop and queen, but also the pawn. This wall can be great for defense. Or for rooks, this can be great for attack, as you can target 2 parallel lines from there [1] For the blue pivots, you have the opposite, as you have more than 1 diagonal. So if you have a bishop, it can go in 2 directions from this corner. I invite you to try the tutorial that opens up when you load the demo, it has a couple steps which illustrate those. Or maybe you have gone through it, and it's not clear enough? I'd be very happy to hear any feedback on this. I have a feeling this info could be more obvious, and that may not be the case yet. And for the board generation, I'm completely open about it. It's actually inspired by a game called Townscaper, and the author generously shared how he made it. I'm merely running with it. I've just written this short explanation on r/proceduralgeneration [2], which I'm copying it here: ------- The game is built using Threejs, Vuejs, and Polygonjs (my own 3D engine based on threejs). You can see examples of scenes where this type of grid is created [3] and the core library is open source here [4] You can also see the code for the most important node, called quadrangulate [5] In short, it takes a bunch of triangles, and convert them to quads by grouping them in pairs. This conversion is straightforward when the triangles are neatly aligned and you process them in order, and the output would then be a very regular grid. But if you process them out of order, you will en up with isolated triangles that have no more neighbouring triangles. Those can't be converted to a quad. But if you subdivide the whole thing, you then get an irregular grid like the one above. ------- What I forgot to mention is that after the subdivision, you may also need to apply a smoothing, or squarification, where you iterate several times of the whole grid to transform the tiles from a rhombus to be more like squares. And you're absolutely right, I should do a blog post about it. It's a question that comes up very often as well, it could do with a central place. And I'd love to see more people using this system, as interesting mechanics emerge from it. [1] https://x.com/fradingue/status/1796892307523830068/photo/2 https://x.com/fradingue/status/1796892307523830068/photo/2 [2] https://www.reddit.com/r/proceduralgeneration/comments/1d5np8w/chess_twist_a_mindbending_chess_variant/ https://www.reddit.com/r/proceduralgeneration/comments/1d5np... [3] https://polygonjs.com/gui/irregular_quad_relaxation/edit https://polygonjs.com/gui/irregular_quad_relaxation/edit [4] https://github.com/polygonjs/polygonjs https://github.com/polygonjs/polygonjs [5] https://github.com/polygonjs/polygonjs/blob/master/src/engine/nodes/sop/Quadrangulate.ts https://github.com/polygonjs/polygonjs/blob/master/src/engin...
- gus_massa 2y ago
  > I need 3 or 4 colors, and in some cases I need 5 4 should be enough https://en.wikipedia.org/wiki/Four_color_theorem https://en.wikipedia.org/wiki/Four_color_theorem, but the alternating color in the border may be a problem. It's an interesting variant for nerdsniping. I guess it's possible to find a 4 color version but it may need too much backtraking. --- > I invite you to try the tutorial that opens up when you load the demo I didn't notice. It's linked at the top. You may add another link at the bottom for people like me that skip the headers. I'll try later. --- About the new strategies, in human vs computer the knight forks are probably more OP than a bunch of blinkstackers with infinite APM. I'd trade a rock or even a queen for a knight just to give my brain some rest.
  - frading 2y ago
    Yes, someone else here mentioned the four color theorem, and that gave me a few ideas to improve that. For the demo, it actually opens up when you start the game. But it's possible to skip it, which is totally fair, I should have expected that. I'll make the button more obvious, you're absolutely right that it's too hidden at the moment. > knight forks are probably more OP than a bunch of blinkstackers with infinite APM There are too many words I don't understand here to infer your meaning. The knight forks I know are when a knight threatens the king and another piece, but it looks like you mean something else. It could be related to what I mentioned with multiple diagonals, although that does not affect knights. And OP is probably not original poster. And I don't know what bindstackers or APM are (maybe Actions Per Minute?). But it does look like you know more about chess than I do, so I'd love to absorb that knowledge.
    - gus_massa 2y ago
      > There are too many words I don't understand here to infer your meaning. Sorry, I watched too many videos of StarCraft 2. OP means Over Powered, i.e. an strategy that is imposible to beat. % years ago, Google made an AI bot to play StarCraft 2, and they made a demo against two proffesional players. The bot was "cheating" so the bot has vision of the whole map, and the bot could make as many "clicks with the mouse" as it wants (APM "action per minute"). The bot discovered an estrategy that was to create some robots with lasers "stalker" that can shoot from a distance, so many of them can atact the same unit. And use an upgrade "blinck" so they can teleport a short distance. So the bot could make all of them atack and pick the hurt units and teleport to the back so the heal while continue atacking. A human can only manage 5 or 10 of them together, and there is a high chance of forgeting to send one to the back. The bot used like 30 of them, atacking from different angles. There is a video with clips of the game. The most clear fight were the bot (in blue) use the trick is https://www.youtube.com/watch?v=6EQAsrfUIyo&t=510s https://www.youtube.com/watch?v=6EQAsrfUIyo&t=510s --- I tried the demo. The default player is too weak. It makes too many silly mistakes. The harder players is hard. I'll try again tomorrow. (The bishops that bounce against the walls when there is a corner with 3 squares in the border are weird. Also, bishops are too easy to block by "walls". I like knights better.)

tromp 2y ago

Making Go Twist is a bit more straightforward, since the rules work unchanged for any undirected graph. Such as this diamond lattice [1] in which inner points still have 4 neighbours. [1] https://en.wikipedia.org/wiki/Go_variants#/media/File:VirgilGriffith.jpg https://en.wikipedia.org/wiki/Go_variants#/media/File:Virgil...

frading 2y ago
Ah that's interesting, thank you. Especially as Go is the one I'm the most unsure about, mostly because I've rarely played it. I have a feeling that making a semi-decent bot is going to be extra difficult. Or at least I'll need a better intuition of what a good bot would do first.

paipa 2y ago

Very cool! Looking forward to playing it. I suggest to minimize visual clutter, because any new player's brain will be overloaded trying to figure out a board, and less is sometimes more. I'd remove the forward direction triangles where they can be unambiguously inferred from the baseline. A lower grain contrast wood texture might be a good idea too. You mentioned you sometimes use five tile colours but you can probably improve it: yes, the four colour theorem guarantees that :)

frading 2y ago
Yes, minimizing clutter was a priority, and still is. I've tried to avoid those arrows for a long time, but the pawn movements wasn't clear enough without them. And I agree it's not the optimal display. Displaying them on some tiles only is something I have not thought of. My first reaction is that it may feel harder to read, as tiles with an arrow may look like they would act differently than those without? We may induce the idea that it has a different purpose. So for now, I'd prefer a solution that would look the same on all tiles, I think that's much easier to parse. But then I should probably give this a try before rejecting it. You do have a good point regarding the wood texture, I've tried other textures, but couldn't find a better one yet. But I'm sure that's possible. Nevertheless for now, you can also display different skins: https://imgur.com/a/zitKlpz https://imgur.com/a/zitKlpz And thanks a lot for mentioning the four colour theorem. I'm looking at its wikipedia page now. I'm sure I came across it many times before, but I did not think about it when tackling this part of the problem. My implementation is here is anyone can spot my mistake: https://github.com/polygonjs/polygonjs/blob/master/src/engine/nodes/sop/QuadUniqueNeighbourId.ts https://github.com/polygonjs/polygonjs/blob/master/src/engin...
- wizzwizz4 2y ago
  The five-colour theorem was first proven in the late 19th century. The known proof of the four-colour theorem is non-surveyable. There's probably no small mistake in your implementation, and the solution you should go with is unlikely to be a fully-general algorithm. (I'd suggest starting from the border on the outside, greedily filling in as many choices as are forced (up to isomorphism), then randomly choosing a candidate breadth-first or depth-first until you've found a four-colour solution.)

jncfhnb 2y ago

Pawns should probably have a piece that indicates their orientation. As far as I can tell it is impossible to discern which way a pawn moves without querying the ui.

frading 2y ago
There are those little black and white arrows on each tile, which indicate which way is forward for a specific player. Does that help? Or maybe you saw them and you mean something else? Interestingly, someone here mentioned that those arrows add a lot of clutter, and someone else on twitter said they only noticed them after I pointed them out. It's interesting how people perceive things like that so differently.
- lucasmullens 2y ago
  It might be worth considering just changing the rules for the pawn to deal with this. It's hard to tell what it means to move "forward" on a board like this, even after understanding the indicators. Maybe pawns could just move horizontally/vertically and attack diagonally, regardless of color?
  - frading 2y ago
    That's an interesting suggestion. The pro is that it will simplify things, remove visual and cognitive clutter. The con is that we stray away from classic chess rules, which I'd still like to avoid as much as possible. I will think about it. It may be possible to allow as an option.
    - paipa 2y ago
      Your constraint should be that if the board is the special case of regular chess, the game should play exactly the same. Allowing the pawn to move towards any side is too much because it would violate this principle. Perhaps define forward as the direction(s) which, when extrapolated as a rook, would reach the opponent's backrank. If it doesn't exist, the direction(s) which, when extrapolated, terminate on the opponent's half. This would allow extra freedom to pawns in some funky topologies that can occur in your game, but generally follows the principle of least surprisal.

deleted 2y ago

[deleted]

SamBam 2y ago

This is very cool, I'm enjoying it. One small note: I tried to castle, and was told "Castling is not allowed because your king was previously in check." This isn't one of the rules of castling in regular chess. [1] Also, it would be nice to implement the three-same-position draw, since I got trapped in a cycle of just moving my king back and forth forever. 1. https://en.wikipedia.org/w/index.php?title=Castling#Requirements https://en.wikipedia.org/w/index.php?title=Castling#Requirem...

frading 2y ago
great to hear, thanks a lot! Thanks a lot for the correction regarding castling. I did look up this page a fair bit when implementing this, and I swear I had seen the rule that castling wasn't possible if the kind had been in check. But looks like I was dreaming. So I'll fix that shortly. For the three-same-position draw, yes, it's on my list. It was really low priority, but your comment makes me move this up the list. I had improved the bot so that it would be better during the end game, thinking that would avoid the need for this rule, but it looks like that doesn't work all the time (which shouldn't be surprising). So yes, I'll work on that as well, That's great feedback, thanks a ton.
frading 2y ago
I just fixed the castling bug. Thanks a lot for letting me know.