The Backgammon by UNBALANCE

 I was looking forward to playing “The Backgammon”. After all, it’s by UNBALANCE, the company that created “Crazy Stone Go”, which was the best Go-playing app for Android/iOS before the AlphaGo clones came. I’m still playing most of my Go games with UNBALANCE’s nice app, and so I expected a lot from a backgammon of these developers.

To some extent I was not disappointed. “The Backgammon” is a solid implementation of Backgammon; unlike many of its competitors it features money games and matches up to 15 points, correctly implements  everything including the Crawford rule, allows to try out different moves before committing to one etc.

I like “The Backgammon”’s presentation. Two different nice boards wait for you, nicely rendered on phone and tablet. The menu system is easy to understand and has a clean, professional look.

The wood board on an iPad Pro 

The app offers both online playing (which I haven’t tried - there’s backgammon galaxy and backgammon heroes with XG-based analysis features) and playing against an AI. This AI offers five difficulty levels from “gruesome gruesome beginner” to “beginner”. 

I must confess I’m disappointed by UNBALANCE’s effort to build a Backgammon AI. Other than their Go this is no master. Even on its hardest level 5 it makes obvious beginner mistakes, like doubling with a checker behind a 6-prime, just because it’s 10 pips ahead in the race. Also its checker play is doubtful at times. I haven’t fed a match into XG, but I am very convinced it plays not better than a PR of 20 or so. Here’s a few examples:

Beginner cube handling at work

In the example above, black has a checker on the bar, behind a 5 prime, and has nothing. But because I’m only 9 pips ahead in the race, it accepts my double.

A horrible double blunder on (iPhone)

To increase longevity and give you a challenge, “The Backgammon” includes a “challenge mode”, in which you have to beat every level at 5 different match lengths to earn medals. Unfortunately, though, Level 1 is so incredibly weak that I can’t get myself to try out what happens if I win all medals (it leaves direct shots without any reason).

The challenge mode (iPad pro)

So, if you’re an intermediate player or better, you probably won’t find an opponent that can offer you exciting matches here. But for beginners, this is an acceptable Backgammon that you can have a great time with, for free. “The Backgammon” is purely ad-financed. It shows you ads on the top of the screen, and will show you an ad movie after each match. There’s no in-app purchase to get rid of the ads.

The alternative green board, also nicely rendered

Please note, though, that an app playing on this level cannot teach you to become a better player. Not because there is no tutor mode, and also not because it just doesn’t play well enough to be a good teacher. For this you need e.g. XG mobile, True Backgammon, Backgammon NJ.

Yes! My first 7-point match played with "world champ" rating

 Okay, you probably couldn't care less, still I'm proud as hell.

Played a 7-pt match against XG mobile today, managed to win and not mess up too badly; finished with a PR of 2.03.

Here's my single blunder. Would you have done better?

White to play 42.

It's fairly clear that the 2 should hit with 16/14*. But what to do with the 4? Move on with 14/10 and minimize risk, or play bold and slot with 8/4?

...

Honestly I should have seen that. I'm 62 pips ahead and should have played safe. 16/14*/10 only leaves two shots - 44 and 64. I went for 16/14*, 8/4 and blundered 0.18 of equity.

Still: YAY WORLD CHAMP MATCH! :-)

A seemingly easy position (or: why I love backgammon)

Came across a wonderful backgammon position today (on DailyGammon). At first glance, it is totally trival. All the complications are gone. In three rolls the game will be decided. 

Still I managed to squeeze a blunder of nearly 0.2 equity out of it. After 10 minutes of thinking. With a piece of paper. And a calculator.

That's how mysteriously complicated backgammon can be, even in its most simple positions.

Here we go:

 

White's turn. Cube action?

 

This is a match to 15, score is 2:2.Should white double? Should black take?

I have still not figured out how to solve this one.

What's your suggestion?

 Spoiler starts here.

The trivial part is: 

• if white rolls 44, 55, 66, white wins (1/12 probability)
  
• if white rolls something else, and black rolls a double, black wins (11/12*1/6 probability)
• if white rolls something else, black rolls no double, then black has only a single checker on 1 and will win for sure. Unless white can bear off the three stones in two rolls.
  But how likely is this?

I was black, my opponent (correctly) doubled.

I arrived at the conclusion that I need 25% wins to take, the second dot gave me only 15%. So I need to win about 10% of all games in case 3. Since even with a 21 roll, white still has many combinations to win, I concluded that nearly all 2-roll combinations will bring the three checkers home and passed.

Tuns out, the correct cube action is double/take. In this position, black will win almost 30% of games (28,97%, actually; I even did a rollout).

I still have no clue how somebody might solve this OTB. And I'm still amazed that such a simple position is so difficult to solve.