Dr Eric Silverman

As promised, today we’re going to take a look at TwixT — a classic connection game designed by Alex Randolph in 1962.  Twixt (I’m giving up on the second capitalised ‘T’ because I’m just going to keep forgetting it anyway) is one of the relatively rare connection games that actually was released in physical form — and copies are still readily available via Ebay and used board game sites.  I have a copy of the 1962 3M bookshelf edition, which looks like this:

The game is played on a 24×24 square pegboard, and each player is armed with 50 pegs of their colour — Red or Black — and 50 bridges that span between those pegs, as in the photo above.  Each player strives to complete a continuous path of linked pegs reaching connecting their sides of the board.

So far, so similar, right?  But what sets Twixt apart is that, despite the seemingly enormous size of the board, games resolve quickly — and fiercely.  Twixt is a highly tactical game — David Bush estimates that the game is about 80% tactics on the standard-size board — and the tactics are razor-sharp.  By that I mean a single mistake can be very costly in this game, and sometimes what constitutes a mistake isn’t immediately obvious.

The upshot of this is that Twixt rewards careful play, deep calculation of possible continuations of each move, and substantive study of tactical principles.  It’s a tense and exciting game, and in my opinion one well worth learning.  I can’t possibly cover all of the myriad complexities of Twixt in one post, of course, and I’m only a beginner myself, but luckily 3-time Mind Sports Olympiad Champion David Bush has helped me tremendously by providing general tactical tips — with examples! — and a fully-annotated game on a small board.

We’ll start with the rules and an overview first, then we’ll move on to tactics, and finally the annotated game.

The Rules of Twixt

Like the other connection games we’ve covered, Twixt is quite easy to learn.  This is how it works:

1. The Red player plays first.  After Red makes their first move, Black may invoke the swap/pie rule on that move only — if Black chooses to swap, they are now Red, and Red now becomes Black and makes Black’s first move.  Alternatively, players may swap and keep their initial colours by reflecting the opening move across the main diagonal and replacing the peg with a Black one, then playing on from there.
2. Each turn, players may do the following:
   1. Remove as many of your own links from the board as you like — usually not necessary, but sometimes helpful to clear up the play area somewhat.
   2. Place one peg of your own colour in any vacant hole on the board, except your opponent’s border rows (the single rows behind the lines of your opponent’s colour, as seen in the picture above).
   3. Place as many legal links of your own colour as you like.  A legal link is available when two pegs are one ‘knight’s move’ apart — in other words, they are at opposite corners of a 2×3 six-peg rectangle.  No links may cross each other.
3. The first player to connect the sides of the board marked in their colour with an unbroken chain of links wins the game.  If neither player is able to do this, the game is a draw.  Draws are very uncommon in Twixt, generally speaking.
4. Players of different skill levels may elect to play a handicap game, in which the stronger player concedes a starting advantage to the weaker one.  The smallest handicap, for use between two players rather close together in strength, would be to allow the weaker player to take the first move while denying the stronger player the option to invoke the swap/pie rule.  From there, players may elect to use row handicapping — here the weaker player’s two sides are moved closer together by removing some rows from the board, making their task easier.  In these games the weaker player is always Red and always plays first.

Note that the annotated game from David is a row-handicapping game, which will nicely show off this excellent feature of Twixt.  Relatively few connection games have straightforward options for handicapping between players of disparate ability; Twixt’s row handicapping makes these kinds of matches just as tense and exciting as any other!  Row-handicapping is supported in real-time Twixt play on igGameCenter, too.

Another nice property of Twixt that it shares with most connection games is its scalability.  The default board is of course the 24×24 pegboard shown above, but the game plays well on both smaller and larger boards (within reason).  Little Golem has recently added options for play on 30×30 and 48×48 boards, and as with other games like Hex, larger board sizes add extra strategic wrinkles to a game of Twixt.  For a very detailed preview of 30×30 Twixt, do take a look at this deeply annotated game by David Bush on BoardGameGeek.  David says this about 30×30:

In a standard game, a player might make four or five moves, usually in the opening, which are based mainly on intuition. The rest of the game is spent attempting to tactically justify the plan you are now stuck with. A larger grid allows a much greater variety in the shape of your strategical plan, and offers a better balance between intuition and calculation.

Having said that, for the beginning player, it may be worth starting first at a smaller size — say 18×18, or a handicap game with a stronger player — before graduating to standard 24×24, then think about trying games on larger grids once you become well-acquainted with the standard board.

As has become my custom in this series lately, I’m going to show you a few final positions of some Twixt games below so you can get an idea how a game might look.  First, let’s take a look at a 24×24 game from Richard’s PBEM Server:

In this game Red resigned after 41 moves, and we can clearly see why — Black has a continuous, unbroken connection across nearly the entirety of the board, and will easily finish a complete connection within a few moves.  Red made a fairly scattershot attempt to block Black’s progress, but ultimately Black was undeterred and deftly slithered straight across the middle of the board.

Here’s another 24×24 game, this time a more intense tactical battle:

This time Red resigned after 57 moves — this is quite long for a Twixt game!  Clearly both sides made several abortive attempts to get a strong connection going, and the battle raged across most of the board.  Ultimately Black was able to find some order amongst the chaos, building up the circuitous connection we see at the bottom of the board.  Red sensibly threw in the towel at this point, as by this point Black has a stronger connection as well as numerous ways to stymie any attempts by Red to get something going.

Let’s take a quick look at one more 24×24 game — this one was played on Little Golem between David Bush and a strong AI called TwixtBot.  This game was played at a very high level, far beyond my ability to talk about sensibly, but you can take a look at some detailed analysis of this game on its entry at the Twixt Commentator website.

Twixtbot is playing White — Little Golem uses White and Black instead of Red and Black –while David is playing Black.  Black resigned here on the 50th move of the game (White’s last move is highlighted in red).  Again I’m not able to analyse this game in detail, but you can see that despite Black’s hold on the centre of the board, White has been able to cut off Black on the left and prepare the ground for a connection along that edge of the board.  I recommend taking a look at the game via the link to Twixt Commentator above — when you step through the moves one by one, and click through the variations in the comments as well, you can get a taste of how intricate Twixt tactics can be at high levels of play.

Finally, since I’ve already linked you through to David’s deep commentary on a 30×30 game, I’ll briefly show off a sample game at 48×48.    Now, 48×48 games are long, and not commonly played, and this particular game has nearly an 800-point rating difference between the two players, but nevertheless you can get an impression of how challenging games at this size will be:

White was the player with the sizeable rating advantage, and in the end Black resigned after 72 moves.  White clearly had the upper hand here from the beginning, and lived up to their rating by methodically winding their way through Black’s defences.  48×48 has yet to achieve the growing following we see for 30×30, but I hope at some point it does take off a bit more — I’d be fascinated to see what pitched battles between strong players would look like on this enormous playing area.

Twixt Tips for Beginning Players

Now I’m going to turn things over to David Bush, who has kindly offered up some useful core principles for new Twixt players:

• The ONLY way to win is to block your opponent on the whole board. More so than with most other pure connection games, there is a difference between making a nice pattern for yourself and blocking your opponent. The latter should always take priority.
• Play lightly.  Just because you put some pieces on the board does not mean you have to use them in your final winning path. Be ready to start a new path if the opportunity arises.
• Focus on tactics.  Try our hand at these interactive puzzles which can occur in a real game.  In my opinion Twixt is at least 80% tactics.
• NEVER play Twixt before breakfast.

Let’s take a bit of a deeper look at some of these points.  Note that these examples below are quite sophisticated, and perhaps challenging for a new player.  I recommend following along with some helpful Twixt software like JTwixt (needs Java to run), which will allow you to place moves on the board and try possible alternate variations, or T1j (also needs Java), which is less full-featured when it comes to analysing games but includes a computer opponent to try your moves against.

The Only Way to Win is to Block

Here is a typical opening position:

Black has just played i14. In the game, Blue answered with K11.

This 3-3 relationship with H8 is called a tilt setup — Blue can make a single move that connects these pegs in two different ways. This is all well and good, but it’s too slow for Twixt. Black played N16.

This 5-2 relationship with i14 would take two moves to complete a connection, but such a connection can form in a variety of ways. You can see the network of possible linking paths is like a diagram of a cube. This is a very resilient pattern. It is difficult for Blue to find a way to attack through that gap. Blue tries to block on the right with P16.

You can see that P16 is on a line that leads to W2. Black could start a race toward the upper-right corner with P15 — a ladder chase — but Blue could simply follow that line to W2 and win the chase.  But Black N12 is much stronger.

Black has a commanding advantage here. Instead of K11, blue might have played O13.

This is not as well connected to H8 as K11 was, but that’s not as important as stopping black from achieving an easy win through the middle of the board. Blue has threats now to connect O13 to the top and to the bottom. This is a much more balanced position.

Play Lightly

This position is from a game between two versions of a Twixt bot. The bots are crushing heads these days. At least one human is probably still stronger as of Spring 2020.

Black abandons its pegs at F4 and L5 to start a new battle along the bottom. A couple moves later we get this:

To a player with some experience, S21 looks doomed. But that’s the point. S21 is a feint, a threat that blue has to respond to. As blue keeps adding pegs to the bottom right, black will improve its connection to the left, and then switch to an attack elsewhere along the right edge. Here is the game several moves later:

Blue’s group in the bottom right is almost useless. Black gave up pegs at F4, L5, and S21 for the sake of gaining an overall advantage across the board.

Here’s a more typical example. Note that the blue borders are on the left and right here.

This 4-1 blocking pattern between i6 and E7 is often the best way to conduct a corner battle. Black is willing to abandon the i8 group in some variations, in order to gain an attack down the left edge. A few moves later we get:

For black, a win via E16 is just as valid as a win via J11.

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Hopefully you could follow along with David’s examples here — as you can see, Twixt has a steep learning curve due to the sharp tactics involved, but the end result is a game with dynamic and exciting play.

Annotated Game — Zurround vs David Bush

This is a handicap game on a small grid, annotated by David Bush.  Red (Zurround) has to connect across 17 rows; Blue (David) has 18 columns to deal with.

A quick note on the move notation — for each move, we simply write the location of where the new peg was placed on the grid.  Since links are generally added automatically in most Twixt online clients or software you might use, it’s normally not necessary to specify which ones are added.  On occasion though you may need to change links around depending on the server — Game Center for example — so in those cases, if you need to understand the notation there is a quick guide on the page of interactive Twixt puzzles.

1. H9   2. H13

3. M11

M11 is an excellent way for red to press his advantage. It makes many threats to connect to the top and to the bottom.

4. L8

5. J10   6. H5

Blue is forced to open up a new front, but he may be able to use H13 later.

7. J6       8. K12

9. L13   10. M5

11. L7   12. N7

13. i4    14. J9

Blue threatens to punch through along the top, at i7, or along the bottom, at L10. Red might be tempted here to play J8 which is a double linking move. But this does not answer both threats that blue is making.

I said that blue was threatening L10, and he is, but it would be a mistake to play there immediately.

Here red can win with H14.

Red threatens to double link at i12. We look at three variations here. The first is i11 G12 G10 F10:

The second is i15 G12 G14 F14:

and the third is G15 i12 i14 J14:

So, instead of L10, blue should play at L14.

This is better than L10 because it still makes two threats to connect to the right, L10 or N13, and guards against red’s H14 threat. We will see how later in the game continuation. We return to the position after blue J9.

In order to win here, red needs to play the same sort of trick that blue played with L14 in the previous variation. Blue used the space available on the bottom right. Red needs to use the space available on the left.

15. F8

Very good move. Red covers both of blue’s threats with a single move. The F8 group threatens to connect to the top in two ways, and to the bottom in two ways.

16. L14

Red could have won here with F13.

One possible continuation is i7 F4 F12 E11:

It almost looks like blue could do a “pincer attack” here with E8. But it doesn’t quite work after E8 D7 G9 E9:

Returning to the game:

17. H14    18. G15

Now blue is winning.

19. i12    20. i14

21. C14   22. D12

23. N14

Red sets a trap. If 24. L10:

25. i14   26. K15   27. L15

But blue sidesteps the trap.

24. M16

25. D11    26. E10

27.Resign

Next steps

From here, I suggest getting out there and playing some games!  After gaining some experience and putting these tips to the test, a good way to continue learning would be to check out David’s articles in Abstract Games magazine — in Issue 2, he provides the rules and a deeply-annotated game; in Issue 4, he covers basic tactical concepts and setups; and in Issue 7 he covers more details on how to battle for dominance in the corners.

There are several good options for playing Twixt online.  Probably chief among these is Little Golem, a correspondence game server which houses a dedicated Twixt community full of strong players, and the site supports the 30×30 and 48×48 variants as well.  Every game has a link next to it to enable you to analyse it on the Twixt Commentator website, which is also a convenient feature.

Note that Little Golem uses the TwixtPP rule set; PP stands for ‘pen and paper’, and these rules are actually the original rules for Twixt before the physical sets were produced.  In TwixtPP, your own legal links are placed automatically after each move by the server and are never deleted, and your links can cross over each other — but note that crossed links do not count as connected!  In practice, these minor rule differences don’t have a huge impact on play, but there are some rare situations where they do change things somewhat, so keep an eye out for those.

Also, this serves as a helpful reminder that you can play Twixt using pen and paper!  Just download and print some boards on a sheet of paper and draw your pegs and links using different-coloured pens or pencils.  This is a great way to try out the game without investing in a set.

You can also play Twixt on Richard’s PBEM Server — you’ll need to read the various FAQs and such to get started, but once you get past that you can play games graphically via the web interface.  This server supports games up to 40×40, and row handicaps of up to 18 rows.  Here the rules are those of the physical game, not Twixt PP; however, the server does automatically place legal links for you, which is helpful.

If you’d rather play Twixt in real time, igGameCenter is a great option, as mentioned above.  GameCenter supports row-handicapping as well, which is great for new players — David and I have played a few handicap games there and they were profoundly educational.  The board by default is drawn in a rather tiny resolution, but pressing Ctrl and +/-allows you to change the display size.  You can step back through your games afterward by clicking around in the move list, though analysing games in detail is probably best done by entering the moves into JTwixt on your own.  On the whole it’s a great place to play real-time games.

Summing Up

So that, in a nutshell, is Twixt.  I’m very much a newcomer to the game, and faced a trial-by-fire in my first matches by facing David right off the bat!  However, our games were not only educational, but also showed me that Twixt is challenging, filled with tension, and clearly can be a ‘lifestyle game’ just like Chess, Go, Havannah, or Hex.  I highly recommend trying it — the steep learning curve means it may not be for everyone, but if it is for you, there is a tonne of depth for you to discover and enjoy.

In future posts I’ll be covering some other interesting connection games with some unusual qualities: Onyx, a connection game played on an Archimedean tiling with captures; Gonnect, a connection game played using the rules of Go; and Slither, a recent invention combining placement and movement to generate shifting, snakelike connections across the board.  I’ll also be covering ConHex and the related meta-rules — rules that can modify almost any connection game — invented by Phil Bordelon.  Please look forward to those!