Basic Strategy Dots and Boxes
9 replies. Last post: 20051026
Reply to this topic Return to forum
KnoxB (Computer) at 20051025
The following is by no means a comprehensive strategy guide. It is instead intended to enable beginners to get up to speed so that they don't feel completely lost as to what they should be trying to do. And after learning the following, you can now play against your buddies who don't know the long chain rule and beat them every time. :)
A Vitally Important Endgame Trick
Suppose it is your turn in the following position.
**** *** * **** ****
Your opponent has just moved at the right end of the bottom chain of boxes. All or almost all beginners take the entire chain and then play some move in the remaining chain.
**** *** *  ****X X X ****
Your opponent takes all the remaining boxes and hence wins 6 to 3. But there is a better way. You should start by taking the first box as before.
**** *** * **** X ****
But now instead of taking the remaining boxes, you make the following doubledealing move.
**** *** * **** X ****
The point of declining the last two boxes in the chain is that your opponent is forced to open up the 6chain (chain of 6 boxes) regardless of
whether your opponent takes the two offered boxes. Your opponent should take the two boxes, otherwise you will take them on your turn. A single move that takes two boxes is called a doublecrossed move (these are critical to the mathematical theory of the game). After the doublecross move, your opponent opens up the last chain.
****  *** * ****O O X ****
Now you take the last six boxes. Hence by doubledealing, you changed a 3 to 6 loss into a 7 to 2 win!
A chain containing three or more boxes is called a long chain. Whoever can force their opponent to be the first one to play in a long chain is said to have control. Now if you have control, you can maintain it by declining the last two boxes of every long chain except the last one (you should take all of the last chain). If there are long enough chains around, then you win by getting and maintaining control up to the end.
For example,
************************ ***** * ******
Your opponent has just opened by uppermost chain. By doubledealing on the first three chains opened up, you give away 6 boxes (two per chain) and you get all the rest for a resounding 19 to 6 victory. If you had instead simply traded chains back and forth like a first time player, then you would have lost 15 to 10.
This suggests the following strategy. Make sure there are long enough chains around and get control.
Getting Control – The long chain rule
If the number of initial dots plus the number of eventual long chains is even, then the player whose moves first has control, otherwise (is odd) the player who moves second has control.
On littlegolem, the game has 6x6=36 dots. Red goes first and blue goes second. Hence, the above general rule simplifies to the following.
The red player has control if the number of long chains is even.
The blue player has control if the number of long chains is odd.
This rule assumes that there are no early doublecross moves. Each doublecross move switches the desired parity in the remainder of the game. (You don't have to worry about this until you learn about various sacrifice plays).
Cycles
Sometimes the ends of a chain meet up forming a closed circle or cycle. For the purposes of the long chain rule, cycles do not count as long chains. Now suppose you have control and your opponent has opened up a cycle instead of chain.
****  * ** * ****
As in a long chain, can you decline some boxes and still maintain control? Yes you can, but with cycles you need to decline four boxes not two. So in the above 6cycle, you
take two of the boxes (it doesn't matter which two you decide to take).
**** X X * *** ****
The doubledealing move for cycles is to split the last four boxes in half forming two 2chains.
**** X X * ***  ****
Now your opponent is forced to open the next cycle or long chain.
Control and Chain/Cycle Length
Maintaining control costs you 1 box for every 3chain (you get 1 box and decline 2 boxes), and nets you 0 for every 4chain. Generally speaking, maintaining control costs you more for cycles than for chains. Of special note is the 4cycle or quad.
*** * * * ***
Maintaining control when your opponent plays in a quad costs you all four boxes of the quad. This is a hefty price when there are only 25 boxes total.
When you have control, you need to have chains that are long enough to overcome the cost of maintaining control. Hence, the player who is going to get control should try to make the chains as long as possible and try to avoid cycles especially quads. If the cost of maintaining control is more than the number of boxes you are going to get, then at some point it is going to pay to relinguish control by taking all of a chain or cycle (this happens more commonly when the opponent opens a cycle than it does for a chain).
Conversely, if you are going to lose control, then you should try to keep the chains as short as possible and try to create a cycle particularly a quad. Even when you have lost the fight for control, you can sometimes squeak out a win just by creating a quad.
Free Boxes: When Greed is Good
There are a few specific situations where it always pays to be greedy and take boxes. It always pays to take free boxes, chains of length 1. Also, it always pays to take chains of length two or three when both ends of the chain are “closed” so that the entire chain is disconnected from the rest of the board.
* * * * ** ** * * *** ****      ** *** * *** ****(A) (B) (C) (D)
In A, we have a free box where the capturing move is at the edge of the board. In B, the capturing move is in the middle of the board – since the box neighboring the capturable one has at least three unplayed edges, the capturable box is a free one. In C and D we have chains of length two and three respectively where both ends of the chain are closed. Whenever you encounter one of these four situations, it is always best to take the boxes.

KnoxB (Computer) at 20051025
The ascii diagrams got messed up. For some reason the
html tags did not work properly – they worked when I made
a separate html page but they don't appear to work when posting to this forum. As a test, here is the first diagram again (the vertical lines should be lined up with the rightmost dots).
****  *** *  ****  ****

KnoxB (Computer) at 20051026
Another test.
***–*
\
*** *
\
***–*
\
***–*
Did it work?

KnoxB (Computer) at 20051026
Yet another test.
With “font” tags
***–*
\
*** *
\
***–*
with “tt” tags
***–*
\
*** *
\
***–*

KnoxB (Computer) at 20051026
One of these tests will eventually work.
This test is for the rather ugly solution (hopefully)
where you specify a fixed font, use explicit codes for nonbreaking space characters, and use explicit break tags.
***–*
\
*–*–* *
\
***–*
\
***–*