Duo to the Death

Blokus has taken over my life

Archive for September, 2009

XF lerpy: is the mirror response bad?

Posted by nand on September 5, 2009

In my initial survey of responses to XF Lerpy the first defensive response is the mirror. My instincts tell me this is not a great response, but it’s far from proven. The usual results of mirroring look like this:

XF Lerpy, P in the centre

(Moves: obviously, X-X, F-F, Z-Z, P.) Why, you may ask, does violet immediately move into the centre on move 4? This is because (1) he doesn’t want to let orange get there first and (2) he’s planning to put a nasty piece through the leak on move 5, typically V5 (J11ddrr).

That V5 caused me to dismiss this line as a disaster for orange, but after playing this out a few times I’m less certain. Basically, it’s an important demonstration of the cardinal rule in Blokus: don’t panic even if things look bad, play aggressively rather than conservatively, and keep a few corners active in as many zones of the board as possible. I played 6 games with myself using variants of this position:

XF lerpy with mirror; violet blasting through the centre

Moves: X-X / F-F / Z-Z / P-Y / V-T. I played the Y below first because it’s important to get something going in bottom left & the Y cannot be blocked in a single move. (It’s a question whether violet V5 is premature–violet could try playing W (I2urur) first, for instance.)

It’s hard to tell from playing versus myself — a live opponent may see angles I’m completely missing — but I basically tried to ensure that orange kept a toehold in all 4 corners, cut off the sides where possible, & generally just was maximally persistent & aggressive. The results were interesting: one big loss, 3 small losses, 2 small wins. That’s statistically pretty good, suggesting that though the violet V5 looks really scary this may be a viable line for orange. More to report on this once I’ve worked out some games more carefully.

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XF Lerpy: initial survey

Posted by nand on September 4, 2009

This is one of the most annoyingly complex openings, & tends to be regarded with exasperation by many players, largely because (1) it’s quite effective; (2) there are a LOT of mid-level players who, once they figure out that this one is pretty solid, tend to play it ALL THE TIME, game after game.  One of my major projects is to dissect this opening to the point where wins are by predictably small, rather than large, margins (rather as with the XF Rubik, XF Tetris-Time and XF Yasu, which are rarely used by experienced players versus other experienced players because the wins are so small they’re not worth bothering with). I have no idea if this opening can be ultimately reduced to a desirably small margin (in my view, 3 points or less) but it’s worth exploring at length.

I think it is worth setting out the plausible orange replies first. These aren’t all the possible replies — I’d be grateful for suggestions of any others I should examine seriously — but they are the commonest, & I think they are worth examining first before testing out others.


1. Mirror

XF Lerpy, orange mirror

2. F to the left

XF Lerpy, orange F to left

3A. N up

XF Lerpy, orange N up

3B. N left

XF Lerpy, orange N to left


4. N kissing violet F

XF Lerpy, orange N kiss

5A. Y kissing violet X, knob up

XF Lerpy, Y kiss with knob up

5B. Y kissing violet X, knob down

XF Lerpy, Y kiss with knob down


My current thoughts: Mirror (#1) is demonstrably bad, as I will show in a future post. F to the left (#2) is extremely effective against low- to mid-level players, but has fatal flaws that can be exploited by good players; it may nonetheless be worth exploring. N up (#3a) has a major vulnerability (violet can wrap Z5 around the orange X) but may be OK; N left (#3b) I am not very familiar with.

The major lines are #4 and #5A/B. My suspicion is that #4 is not good, because violet simply lays down N (B7drdd) and orange has no corners to work with in the bottom left corner. Thus #5A and B are the best options, the major branches depending on whether violet plays through the hole on move 3 (typically with T5, though V5 is an option) or blocks the Y.  If violet blocks the Y then orange has the option of playing the N in the same way as in #4, or playing something else there (typically T4).

I’ll try to pick away at these openings one by one, though it’s a tough job. Anyway who wants to help out, be my guest 🙂 ……

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Bigwood F #2

Posted by nand on September 3, 2009

I’ve been working out orange lines for this one. There are so many lines that lead off it, depending on orange’s first move, that I think possibly its main strength is just that it’s hard for even high-level players to remember all the variations. I suspect it’s not all that strong an opening, in fact, just a hard one to grasp. So my little project is to limit the lines & make this a manageable game for orange.

My current thought is that the best initial move, no matter which way the violet F is turned, is a mirror. This almost inevitably gets a violet Y plunked into the middle of the board, cutting off two orange corners & threatening to cut off more. Here’s one line of response (the L5 move is, I think, mine; the U I’ve seen from other players):

One response to Bigwood F (variation 1)

One response to Bigwood F (variation 2)

Moves: 1. F – F / 2. Y – L5 / 3. N – U. Orange L5 is key here: if it were Y then a hanging violet N (E3uuru) or L5 (E3uuur) would threaten a cut-off on the bottom. There’s no powerful cutoff move for violet on the bottom left on move 3, so violet is forced to threaten on the right side. But once violet N is played, orange U leaves only three unappetizing options for violet: (1) block with L5 (K10rrrd or K10rrru) sacrificing a tempo & the entire bottom right corner plus creating a terribly vulnerable series of sides in violet’s top area; (2) play a kiss move (probably T5 [K10rr]); or (3) play a move threatening a cutoff (e.g. W [K10ruru]). I think option (2) is the only viable one, & I’ve played games with this line that have gone either way.

Whatever move violet makes on move 4, I think orange’s logical 4th move is T5 (E5uur), which forces a response from violet (in order to avoid orange N [C8uuru] on move 5).

I do not think that violet can afford to ignore orange U & attack on the left on move 4; if he tries this, orange should simply play as aggressively as possible on the top. I can try to be more concrete about this line in a later post, if it seems worth pursuing.

Thanks to Dormys fan club & mike_yosuke for playing a few games with me that allowed me to work some of this stuff out.

[UPDATE: Bigwood tells me that the position in the 1st board is correct but he thinks in the 2nd board violet’s Y is positioned wrongly: it should be at H6uuu. Then obviously the violet N is no longer the obvious option…. in the game we played together BW played X there. Obviously I need to work on a sequel to this post.]

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XN Gerenuk #1

Posted by nand on September 3, 2009

Been away from posting for a while, not so much because I haven’t had anything to say but because I’m been working hard at thinking through openings. I’ve decided to try posting more “incomplete” posts, first because it’s often simply too timeconsuming to work a line out to its end, & secondly because I’m not so much interested in “solving” a line as in guaranteeing that it remains open (i.e. that orange isn’t in such a helpless situation that there’s no point in working it out further). I also was hoping that occasional readers of this blog will suggest moves I haven’t considered, so we can collectively crack some of these lines.

As my first installment in this series, here’s my current thoughts on XN Gerenuk, one of those looks-bad-but-actually-is-kinda-good openings that is a frequent headache. Currently Rubik87 seems to like this one a lot, but you’ll see it frequently employed by many other players. It requires some special handling if orange tries to mirror it — unlike the XF Lerpy, where the mirror option is a clear disaster (I’ll write about this in a later post), the mirror option isn’t too bad a choice for orange here, & much harder for violet to crack.

Anyway, my current thinking is that orange needs to avoid the temptation of cutting off the corners of the N. I think W on move 2 is very promising, as follows:

XN with W response, take 1

The moves are fairly obvious: 1. X – X / 2. N – W / 3. Y – Y / 4. L5 – P. I believe that violet Y is a forced move, though there’s one other option I’ve explored below. Orange P could also be T4 if one believes that the extra cell in orange’s bottom right might be crucial for endgame packing — I dunno. — From this position I think violet is forced to play through the bottom leak, probably W (G5drdr: that’s “cell G5, down, right, down, right” if you haven’t encountered this notation before). Then probably orange L5 (K4dddl), and the game gets messy. Messy is generally a desirable situation for orange, but obviously from this point the game has too many lines to follow in this preliminary post.

Here’s another possible line: I’m not sure who devised the tricky orange F move but it’s a smart one.

XN with W response, take 2

Violet has no good block now that I can see, & not even anything that leaves a nice block for later on. Another messy game. I think it’s crucial violet maintain a threat against both the bottom right & top right, so when I’ve encountered this situation in the past I’ve played F (J8urr), since it’s vitally important that orange be distracted on this turn from closing up the bottom leak off violet Y. This is a really tricky position, & I don’t think it favours either player.

XN with W, take 3

The only other option I see for violet other than the Y through the middle is this W. It looks bad to me, as basically violet has no good 4th move… violet needs to do too many things here: attack on the right side (& close off that leak); attack through the middle (& close off that leak).  I think the only option for violet is L5 (J10rrrd), which leaves orange with the option of Z4 through the centre or L5 on the right side…. tricky situation, & I’d have to analyse it further to see who’s on top.

So, food for thought. The other line I’ve been exploring as a response here is a defensive move (again, not my move, but I’m not sure who devised it). I’ll just post this one here for now & maybe follow it up later (or in the comments). The key is that there’s no nice block for violet at this point, but I don’t think violet can just ignore the orange F & play a “wait and see” defensive move on top as orange has some nasty things he can do below (possibly Z5 [D2ruur]?).

XN with an XF defence

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