Senket Introduction and Rules

Background

Senket is a board game I invented several years ago. My goal was to come up with rules as simple as possible, but game play as deep as possible.

Go was my inspiration. The rules of Go are very simple, but there are several complexities:

  • The ko rule can be confusing for beginners, especially since it is implemented/described in several different ways. Snapbacks have to be distinguished from kos.
  • The concept of life and death — simplified, that two eyes live and one eye dies — is so fundamental to the game that, while not part of the rules, no description of how to play is complete without it. Seki further complicates the issue.
  • There are different methods of scoring, although they are nearly equivalent.

That said, Go has perhaps the deepest strategy of any board game ever, and certainly the highest ratio of game depth to rule complexity of any game I know.

Senket’s rules are even simpler than Go’s, as you’ll see below. There is only one type of move, with no special cases. Nothing is ever removed from the board, or moved once placed. At the end of the game, territory is simply defined.

The question of depth of strategy remains open. From a sheer numbers standpoint, Senket is more complex than most other games, but just because the board is bigger doesn’t necessarily mean much. In gameplay, Senket seems deeper than Checkers, and perhaps as deep as Chess, but until/unless world-class games of Senket are played, it is impossible to say.

Description

Senket is played on a grid. Grids as small as 11×11 will work, but 17×17 makes for a reasonable game, and 31×31 is the official size. The goal is to surround more territory with your fences than your opponent. The overall concept is similar to Go. The mechanics of game play are similar to Twixt.

Rules

  • Players take turns making moves.
  • A move consists of placing a post on any unoccupied intersection of the grid (including the borders), and then making as many valid fences as you wish.
  • A fence connects two same-color posts across an open diagonal of a 1×2 rectangle.
  • Once placed, posts and fences cannot be moved or removed.
  • Play continues until both players pass.

Scoring

Territory is any region of the board your fences surround that does not contain any territory of your opponent. At the end of the game each player’s score is the sum of the values of each separate territory. Each territory’s value is the square of the sum of:

  • The area the territory’s fences surround (see below for examples).
  • The number of opposing posts captured within the territory.

Scoring does not take place until the end of the game. You can play inside your opponent’s territory if you think you can make territory there.

How to Move

The blue fences are valid, the red fences are not.

The blue fences are valid, the red fences are not.

In this diagram, all the blue fences are valid. All the red fences are invalid:

  • None of the red fences in the upper right are 1×2 diagonals.
  • The red fence in the lower left does not connect two posts.
  • The two red fences in the lower right are crossed; whichever was drawn second is incorrect.
  • The red fence in the bottom center connects a red post and a blue post.

No Forced Moves

A fence does not have to be drawn just because it can be. The lone blue post on the left can connect to either of the two posts above it. The blue player will decide whether to connect this post on a future move or not. Usually there is no reason not to connect all posts that can be, but there are a few specific circumstances where it is beneficial (or even necessary) not to draw all possible fences.

Scoring Example

A completed game.

A completed game.

This diagram shows a completed game, with each player’s territory shaded in his color.

The area in the lower right marked in yellow is not Blue’s territory. Even though Blue surrounds it, the red territory inside it makes the area inside the blue fence but outside the red fence neutral. It counts for neither player.

The blue post in the upper left magenta territory counts as a prisoner for Red. The blue and red posts in the yellow area are not prisoners, and count for no one.

Red scores:

  • Upper left area: 27
  • Upper left prisoners: 1
  • Upper left value: (27 + 1)^2 = 28^2 = 784
  • Lower left area: 10
  • Lower left value: 10^2 = 100
  • Lower right area: 2
  • Lower right value: 2^2 = 4
  • Total score: 784 + 100 + 4 = 888

Blue’s areas are connected. Blue scores:

  • Upper right area: 19
  • Lower left area: 12
  • Total score: (19 + 12)^2 = 961

Red actually surrounded more territory and prisoners (40 to 31) but Blue connected his territory and won.

Basic Strategy

It’s easier to make territory in the corners, but it’s also important to connect your territory. As shown in the example above, Red took much more territory, but lost because Blue connected and he didn’t. On larger boards this is even more important.

Consider the value of different available moves. As play winds down in one location, there will probably be bigger plays elsewhere that offer a larger reward. This is a careful balancing act that continues throughout the game.

Senket is not a kill-or-be-killed game (as compared to Chess or Checkers). Every game will likely end with both sides securing at least some territory, so look for advantageous ways to divide territory being contested, rather than a way to take your opponent prisoner, unless that’s a real possibility. Think “how can I get more out of this than my opponent?” rather than “how can I destroy my opponent?”

I’ll follow up with examples as I prepare them for the web.

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21 thoughts on “Senket Introduction and Rules

  1. Bilal

    This is really cool, I hope you, or someone, will make a Java/Flash version of this, i’d love to play 🙂

    Reply
    1. gcanyon Post author

      Thanks — I may try to work something up, but it would likely be a standalone application, since my Java/Flash skills are distinctly limited.

      Reply
  2. Soot

    This is actually a perfect copy of the chess-like chinese board game Go. If you haven’t heard of it I recommend it warmly. Its complexity is great, it is 2500 years old and the player base is (of course) huge. You would probably love it. There are several online communities dedicated to playing it and I think OGS is the most well-known one.

    Reply
    1. gcanyon Post author

      Yes, I’ve heard of Go — I mentioned it as an inspiration for Senket 😉

      The two are alike in that the main goal is to surround territory, but the similarity ends there: the moves are different, the definition of territory is different, and the scoring is different. In general I’d say Go and Senket are about as alike a Chess and Checkers are.

      Reply
  3. Alex

    I’m sure someone at elance could help you develop it. This sounds like a really good idea and you should pursue it.

    Reply
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  7. twixter

    I believe we played a game or two of this on a virtual Twixt board on http://www.iggamecenter.com Have you asked Arty Sandler, the administrator and programmer there, about implementing this? His site uses Javascript. He has tons of esoteric abstracts there. Your Senket would fit right in.

    Heh, you could use a Twixt set to play this F2F, but if you use the full size grid you might run out of pegs and links.

    My impression of it so far is that I don’t know what to make of it. It seems way cool, but I don’t know how it will stand up to scrutiny. But that’s the great thing about a site like Game Center- you can playtest your ideas and see how they hold up.

    Reply
  8. gcanyon Post author

    Thanks for the suggestion! I sent Arty Sandler an email. One of the tougher aspects of programming Senket is scoring. I have the mechanics working fine, but scoring is (so far) proving difficult. On a computer it’s particularly necessary to have the computer score, as it would be very difficult to score without being able to mark up the board.

    Reply
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