Duo to the Death

Blokus has taken over my life

Archive for May, 2009


Posted by nand on May 24, 2009

There are several openings which are worthless because of symmetry rules: orange can simply mirror every move of violet’s & produce a tie (or, if violet screws up, a win). W to the centre or Z5 to the centre on move 1 are examples of mirrorable openings. The only way for violet to break the mirror is to be able to force an assymetry at the centre of the board (e.g. by occupying 3 out of 4 of the central squares).

Both of the following are what I call quasi-mirrors: it is not impossible for violet to break the mirror at this stage, but there seems to be no strong move available to violet that would break the mirror. — In the case of the N opening, the only available mirror-breaker is L5 in the centre (violet need not play this on move 2, but needs to keep the space open for the L5 move unless orange stops mirroring first). In the case of the X opening, the obvious move is F into the centre (occupying 3 out of 4 squares), but this seems weak.

Posted in flawed openings, mirroring, openings | Tagged: | 4 Comments »

Basics #1

Posted by nand on May 24, 2009

Know your piece names.


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Achilles heels #1

Posted by nand on May 24, 2009

The holed FY opener comes in two forms, depending on whether the Y is place running down or across. The ideal is for orange to play F or something else into the hole, allowing violet to wrap N around orange X & start squeezing from around the edges. It’s an excellent opener to play against inexperienced or midlevel players who don’t know how to respond. Unfortunately, as far as I can tell, it has a definite solution from orange’s perspective: this is the response devised by Bobby_Bob:

Looks bad for violet...

Looks bad for violet...

You also see Y for orange N, too, though I haven’t worked it out. Orange’s obvious moves are W curling around the top or bottom.  I’d advise hanging on to F, as that’s the best block on the top if violet plays W above.

If there’s an obvious flaw in the logic here, please tell me.  (The N is weak, for instance, but I fail to see a stronger move.)

Posted in flawed openings, FY open, openings | Tagged: | 5 Comments »

Studies in backstepped F #1

Posted by nand on May 24, 2009

The "delayed" F opening, take 1

The "delayed" F opening, with a double-block

The usual idea with this opening is for violet to wrap N around orange X on move 3 (killing a bunch of corners) & then keep squeezing. There are basically two approaches for violet to this opening (& to many others): circling (i.e. both players keep moving counterclockwise) and blocking (when violet stops the circling with a block — often with a double-block by doing the same thing on the next turn). This game is an example of a double-block, with violet L5 and N.

I have a general theory about this opening: if orange loosely “mirrors” it (i.e. plays a piece on the opposite side from violet rather than blocking, & roughly matching violet’s level of aggressiveness — i.e. match a kiss with a kiss, a hang with a hang) then it’s very hard to lose by a lot, & in fact one can often eke out a win or tie. It’s a 50-50 type of game as long as orange doesn’t panic… I think.

Anyway, here’s one example, caught in the wild. I’ll get around later to discussing the line if violet puts Y or N on top of orange X on move 3. The key here is that orange F creates a nasty trap for violet, because there’s a classic unblockable 1-2 series of holes on the top of violet F. Violet’s strategy may be at fault here — I’m pretty sure violet Y is a mistake, as it’s necessary to close the bottom side (e.g. with T5) to avoid getting the return threat created by orange L5.

Here is the move order:

  1. F – X
  2. X – N
  3. L5 – F
  4. N – Y
  5. Y – L5
  6. Z5 – I5 …. and the rest is self-explanatory.

If violet blocks off the bottom attack then it looks better for violet:

This time violet cuts off the bottom

This time violet cuts off the bottom

I’m pretty sure it’s disaster for orange to block V5 below immediately. Violet would simply play Z4 or P up top to both block the attack off orange Y & staunch the dangerous leak off orange F. Here’s one possible line (probably not ideal) that results in a minor win for violet.

One possible line: 4-pt win for violet

One possible line: 4-pt win for violet

Maybe this would be a point or two better if orange plays L5 above, then T5 rather than L5 in the bottom (I think violet would be unlikely to block the T5 in favour of defending top left), then U and O4 to fill the bottom, Z4 rather than W to fill the hole, & repack accordingly… Choices, choices. (I just tried that — the results are 65-61, the same difference.)

To explore this line more thoroughly we’d need to check what happens with various violet blocks other than T5, & also the possibility if violet plays L4 wrapping around the bottom of orange X. Orange could play L5 not Z4 on top, threatening Z5-I2-I4 down the side of violet’s pieces… the problem here being that if orange really went through with this plan, in the interim violet could make serious (hole-less) grabs for space on the right.


I’m not entirely sure how the game works out if orange plays Y up: but here’s one winning line for orange. Possibly N for violet on top would do better than Z.

Not so good for F... maybe Y would be better than V5 below?

Final score 66 for orange, 60 for violet. Maybe Y would be better than V5 below?

Posted in Oldmanc backstepped F, openings | Tagged: | 4 Comments »


Posted by nand on May 23, 2009

This is a place for me to discuss strategy in Blokus Duo (and other forms of Blokus, too, if I ever get any good at them). If you haven’t already played it, it’s a pure-strategy boardgame with exceedingly simple rules; there is an online version at this link where I go by the handle “nand” (usually ranked in the top 1 to 3 players in Blokus Duo, unless I’m slipping). There used to be a forum on that site, but, while it is still there, it seems to be rather buried ever since Sekkoia (the original game company that marketed Blokus) sold the rights to Mattel, who don’t seem to have a very clear idea of what to do with the game or the site. So it seems a better idea to place my notes on the game here.

Discussion is welcome, and if any avid Duo fans want to create their own posts & threads, please drop me a line & I might (if I’m nice!) create multiple usernames for this blog.

Posted in misc | Tagged: , , | 2 Comments »