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Connection Games V: Side Stitch

We’re back looking at connection games again, and this time we’re going to cover a game invented in 2017 by Craig DuncanSide Stitch.  Side Stitch is a game reminiscent of Star and *Star, where players must make connections between groups touching key cells along the edges of the board.  Where Side Stitch differs from its predecessors is that it incorporates a recursive group-scoring mechanism that ensures there are no draws, rather than using a scoring penalty to encourage the formation of larger connected groups as in Star and *Star.

How to play Side Stitch

Side Stitch is played most frequently on hexhex boards (hexagonal boards tesselated with hexagons — examples below), on which the edges have coloured borders (although other shapes are possible — see the game’s image gallery on BGG for examples).  The number of colour-sides does not necessarily match the number of sides of the board!

The rules are very simple:

  1. Two players, Black and White, take it in turns to place a single stone of their colour on any empty hexagon on the board.  Once placed, stones do not move and are never removed.  Players may also pass their turn.  The game starts with the pie rule/swap rule.
  2. The game ends when both players pass in succession, or when the board is full.
  3. Once the game is over, the winner is determined by the scores for the players’ groups.  Each connected group of same-colour stones gives a score equal to the number of colour-sides that group touches (cells adjacent to two colour-sides count as touching both of them).  Each player finds their highest-scoring group, and the player with the highest-scoring group wins.  If both players have the same score at that point, then they compare second-highest-scoring group, then third-highest, and so on.  Draws are not possible in Side Stitch.

Here are some sample boards I made in Adobe Illustrator based on Craig Duncan’s designs, available for download on BGG:

Side Stitch 7-9-notation-01

Side Stitch hexhex-7 board with 9 colour-sides.

Side Stitch 8-7 big borders-01

Side Stitch hexhex-8 board with 7 colour-sides.  This is Craig Duncan’s pick for the ‘standard’ Side Stitch board, as he feels the 169 hexes allow for a suitably complex game without it overstaying its welcome.

Side Stitch 10-01

Side Stitch hexhex-10 board with 9 colour-sides.

From these sample boards you can see that Side Stitch plays well on wide variety of board shapes and sizes, and with different numbers of colour-sides.  The colour-sides also give the boards a lively and appealing visual aspect.  Craig Duncan recommends the hexhex-8 board with 7 colours-sides as the ‘standard’ Side Stitch board; I tend to agree with him that this board allows for deep and challenging play without dragging on too long.  Having said that the hexhex-10/9-colour board allows for a bit more of strategic battle, and to me is equally as good as the standard board.

The recursive group-scoring mechanism — comparing highest-scoring groups first, then second-highest, and so on until any ties are broken — has appeared in a few recent connection games and related titles, most notably Nick Bentley’s highly successful Catchup (easily my favourite game of his at the moment).  This mechanism works particularly well in Side Stitch — draws are impossible and the winner is very easy to determine.  In combination with the board’s brightly-coloured sides, it makes a strategically and tactically complex game highly readable in play — following who’s ahead is very straightforward.  As a whole, Side Stitch is a fun, elegant and fundamentally flexible game that scales really well.


Side Stitch in play

Despite its simplicity, players discover very quickly that Side Stitch has enormous depth and variety.  As players attempt to stitch the colour-sides together to form the highest-scoring group, they’ll need to pay equal attention to interfering with their opponent’s plans as well.  The need to connect widely ensures that play spans the entire board surface, and strategic concerns remain paramount even on smaller boards.

Here’s a sample game, one of my early attempts against Ai Ai’s MCTS player on the hexhex-7/9-sided board:


The AI is playing Black here, and won with a board-spanning group in the centre connected to five colour-sides.  As this was an early attempt at the game, I was too wrapped up in my own attempts to connect in the opening phase, and failed to counteract Black’s efforts to split my stones in two.  Here’s a GIF so you can see my shame step-by-step:


After several more losses, I took a game from the AI on the hexhex-8/7-sided board.  By this time I’d learned how to balance my attack and defence obligations more appropriately and to manoeuvre a bit more cleverly across the board.  The AI (Black) resigned in this position:


You can see that Black made a valiant, and ultimately successful, effort to block me from the left side of the board entirely.  However, I was able to extend all the way to the top-right corner, which together with the connections on the right and bottom netted me a group scoring 5 points — an insurmountable margin for Black.  Here’s a GIF of the full game:


Now this game is still young, and I’m by no means an expert myself, so it’s difficult to give detailed tactical and strategic advice.  But hopefully these sample games can give you some idea of how Side Stitch feels in actual play.  For me it’s a standout amongst the many recent connection games — it’s easy to understand but affords some very intricate play.  The colourful boards are really appealing, too, and so far the game retains its character and excitement on all the boards I’ve tried.

At a tactical level, connection game basics from Hex et al. will serve you well here; for strategic considerations, you can take some inspiration from games like Star and Starweb.  What’s key in Side Stitch, as in other connect-key-cells games, is to impede your opponent’s progress as well as furthering your own connections.  You also have to keep in mind the recursive scoring mechanism — if you and your opponent are fighting a close battle, then your second- or third-best group may well decide the game!  So don’t forget to develop additional scoring groups, in case the board situation may require a tie-break with your lesser groups.


Side Stitch 6

In response to thread on BGG, Side Stitch designer Craig Duncan designed a way to play Side Stitch using the six sides of the hexhex board, rather than having a different number of colour-sides.  In order to keep the play the same and avoid draws the board ends up being a bit different:


The rules of Side Stitch 6 are the same as in normal Side Stitch, except that the missing corner cells obviously aren’t playable, and each player starts with stones already in contact with each of the six colours.

Personally I’d rather just play regular Side Stitch and try lots of interesting colour combos, but it’s nice that the game still holds together with six sides or other even numbers of sides, with some small adjustments.

IMPORTANT UPDATE: Side Stitch is now playable at the Gorrion Server!  Here’s how the game looks over there — note that scoring is not yet implemented so players have to do that on their own.  So far we have the hexhex-8 board with 7 colour-sides available (Craig’s standard board).


UPDATE 2: Side Stitch 10 — hexhex-10 board with 9 colour-sides — is now also available on Gorrion!




The discussion on Side Stitch 6 eventually lead to the development of a sister game, Exo-Hex.  Exo-Hex takes the next logical step from Side Stitch 6 and eliminates the colour-sides entirely.  Instead, black and white stones are placed outside the boundary of the board — these are called ‘exo-stones’ — and players compete to build groups connected to the largest number of exo-stones.  The win condition and scoring mechanism are the same as in Side Stitch.  The result looks like this:


This new arrangement creates some new wrinkles — the sides are no longer neutral, but are already colonised by pieces of both players.  Also, since the sides consist of stones themselves, the sides are connective — in other words, a chain of stones coming in one end of a given side is still connected to a chain of stones coming out the other end.

Speaking personally, I’d still rather play Side Stitch — it has a level of personality and flexibility/extensibility that Exo-Hex doesn’t.  But as a consequence of this more focussed design, Exo-Hex is easily playable with any standard hexhex board and two colours of stones, and it’s elegantly simple.



Our last game of today is Iris, another 2019 invention from Craig Duncan with links to elements of Side Stitch.  Iris also has a colourful visual presentation and uses recursive group scoring, but uses a different movement protocol.


An Iris sample game — check the game’s image gallery for more of Craig’s attractive board designs

Iris works like this:

  1. Two players, Black and White, take it in turns to place stones of their colour on the board.  Black goes first, and in their first turn may place one stone on any grey interior cell of the board.  After that, players may place two stones of their colour on the board subject to these restrictions:
    1. If a stone is placed on a coloured cell on the outer rim of the board, the second stone must be placed on the corresponding same-coloured cell on the opposite side of the board.
    2. If a stone is placed on an empty grey cell, the second may be placed on any non-adjacent grey cell.  If no non-adjacent cells are available, the second stone may not be placed.
  2. The game ends when both players pass, or the board is full.  Then players score their groups of same-coloured stones; the score of a group is equal to the number of coloured stones included in that group.  The highest-scoring group wins, and the scoring is recursive — if the highest-scoring groups have equal values, then we compare the second-highest, and so on.

I haven’t yet had the pleasure of playing Iris, but the prospect of a connect-the-key-cells game with two moves per turn (this is known as the 122* move protocol) is quite appealing.  The additional move would allow for some complex threats to be made and answered during play, and might further encourage the players to attempt adventurous cross-board connections.  A nice side-effect of the 122* protocol is that the pie rule isn’t necessary; the first player’s single placement at the start balances out the first-move advantage.


Summing Up

Side Stitch and its kin here show us that the design space surrounding the Star/Starweb connect-the-key-cells concept is rich with possibilities.  Side Stitch’s adoption of the colour-sides and recursive group scoring gives it a distinct character from its ancestors, and in play it shines as one of the better connection games I’ve played in recent years.  Exo-Hex and Iris are a bit more focussed in design, which has pluses and minuses — of the two, Iris stands out as having some interesting potential.  The 122* move protocol with placement restrictions adds an interesting wrinkle to this sub-genre of games.

All told, Craig Duncan’s had a productive couple of years!  Out of the three Side Stitch is clearly my favourite design, but if the others become playable via Ai Ai or other venues then that may change.  For now I think Side Stitch offers personality, playability and flexibility, and it’s certainly made it to the ranks of games for which I plan to print a mat and encourage others to play.

Next time, we’re going down a somewhat different route.  I’ll be covering a single game, the classic Twixt, in significantly more detail than the other games I’ve presented here.  This will be possible thanks to David Bush, three-time Mind Sports Olympiad Champion in Twixt, who has not only sent me fantastic content for that post but has given me a Twixt trail-by-fire in some very challenging games.  So do look forward to that post — hopefully you’ll come to the end of it packed with Twixt knowledge and ready for the tactical challenges the game has to offer.


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Funded PhD opportunity at Teesside

Fully-funded PhD opportunity available! I’m looking for someone interested in working on agent-based modelling for healthcare applications. No fees and £20K stipend. These are four-year positions and you will be asked to contribute up to six hours per week of teaching (tutorials/demonstration only, no lectures), which is more work but also good for the CV. Click here and filter under ‘Computer Science’ to see my project.  For more about me, check out the various pages on this blog or my staff profile at Teesside.

Project description: This research will focus on the application of Agent-Based Modelling techniques to human social systems, with particular emphasis on digital health applications. In the context of public health, agent-based models can help us understand the complexities of health policy implementation and service delivery by modelling the multiple interacting processes underlying the health system. These models will investigate challenges in health and social care service delivery across a variety of spatial and temporal scales – from short-term studies of demands on accident and emergency services, to longer-term explorations of the pressures facing social care over the next several decades. Our multi-disciplinary team will work with members of the School of Health and Social Care here at Teesside, along with external collaborators and stakeholders. The project would be suitable for a graduate with a background in Computer Science, Artificial Intelligence, Statistics or Complexity Science with an interest in Public Health/Healthcare applications.

ACADEMIC FRIENDS: Please tweet/share this as widely as you can!

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The ‘invisible army’ of elderly carers

Some of you may have seen my paper with Jason Noble, Jason Hilton and Jakub Bijak from 2013 called Simulating the cost of social care in an ageing population.  The paper presents an agent-based model of informal social care in the United Kingdom.  Our virtual agents live in a simulated UK, and try to live out their lives — moving around, working, starting families, etc. — and when their family members need help due to illness, they try to contribute their time to help out.

Model results showed that, surprisingly, retirement age has a strong impact on social care costs across the population.  When the retirement age was raised, there was a net increase in tax revenues up to a certain point, but beyond that critical limit social care costs began to rise.  The model seemed to indicate that an unexpectedly large number of elderly people were providing informal care to their spouses or other loved ones, and so putting them back into the workforce actually led to increased demand for state-funded formal care for those left at home, increasing the cost to society overall.

I’ve just noticed a news posting from Age UK from last month which is pretty relevant to this:

New figures released this morning by Age UK show there is an army of carers amongst the oldest in our society, who are between them saving the health and care system a massive £5.9bn a year by providing unpaid care.

Over the past 7 years the number of carers aged 80 and over has rocketed from 301,000 to 417,000, an increase of nearly 39%. Now 1 in 7 people aged 80 and over provide some form of care to family or friends.

Furthermore, over half (144,000) of carers in this age group who are caring for someone in their home are doing so for more than 35 hours a week, while a further 156,000 are caring for more than 20 hours a week. As our population continues to age it is estimated that there will be more than 760,000 carers aged 80 and beyond by 2030.

I’m the first to admit that I’m a bit of an outsider when it comes to gerontology and the study of social care in detail, so it’s possible that this study isn’t telling us much that’s new.  It’s news to me, however, and I’m glad to see that our model showed us some interesting results that turned out to be reflective of reality, despite the necessarily simplified nature of the model’s systems.

Now that there’s some solid data out there about this ‘invisible army’ of older carers, I think it may be time to revisit this model and investigate this aspect more fully.  Caring for someone 35 hours a week or more is exhausting work for anyone, let alone someone over 80 years old who should be enjoying a dignified retirement.  Perhaps we can use agent-based models to investigate policies that could take some of this burden away from our older population.

Demographic Research paper is out!

Our paper for the journal Demographic Research just came out today!  After months of hard work it’s so satisfying to see it out there, and we love Demographic Research — they’re open-access too, so feel free to download to your heart’s content and spread it widely.

Next up will be our paper for the Journal of Artificial Societies and Social Simulation; the final version has been submitted to the editor so it won’t be long now.  Always good to have these things done; now we’re able to move on to the next paper!


Paper accepted to Demographic Research

Got the news recently that a paper by Jakub Bijak, Jason Hilton and myself has been accepted for publication in Demographic Research, an open-access journal for demography and population sciences.  We’re very pleased to see our work accepted, particularly as we’re offering up a relatively unconventional approach.

We’ve just sent in the final version for editing/formatting, so it won’t be online for a little while.  In the meantime here’s the abstract:

Reforging the Wedding Ring:  Exploring a Semi-Artificial Model of Population for the United Kingdom with Gaussian Process Emulators

Background We extend the ‘Wedding Ring’ agent-based model of marriage formation to include some empirical information on the natural population change for the United Kingdom together with behavioural explanations that drive the observed nuptiality trends.

Objective  We propose a method to  explore statistical properties of agent-based  demographic models.  By coupling rule-based explanations driving the agent-based model with observed data we wish to bring agent-based modelling and demographic analysis closer together.  

Methods We present a Semi-Artificial Model of Population, which aims to bridge demographic micro-simulation and agent-based traditions.  We then utilise a Gaussian process emulator  – a statistical model of the base model – to analyse the impact of selected model parameters on two key model outputs: population size and share of married  agents.  A sensitivity analysis is attempted, aiming to assess the relative importance of different inputs.

Results The resulting multi-state model of population dynamics has enhanced predictive capacity as compared to the original specification of the Wedding Ring, but there are some trade-offs between the outputs  considered.   The sensitivity analysis  allows  identification of  the most important parameters in the modelled marriage formation process.  

Conclusions  The proposed methods allow for generating coherent, multi-level agent-based scenarios aligned with  some aspects of empirical demographic reality.  Emulators permit a statistical analysis of their properties and help select plausible parameter values.

Comments Given non-linearities in agent-based models such as the Wedding Ring, and the presence of feedback loops, the uncertainty of the model may not be directly computable by using traditional statistical methods.  The use of statistical emulators offers a way forward.