World Class Player level

What "World Class" means here

Every member of the club carries a Level of Play, and the level is not a mood or a slider. It is a measured playing strength, expressed in the number the backgammon world uses for exactly that: PR, the Performance Rating. PR is simple to state. Take every decision a player makes in a match, ask the engine how much each one cost compared with the best play, add it up, divide by the number of decisions, multiply by 500. Lower is better; zero is perfect.

A World Class member's play sits in the band PR 2.5 to 3.5 — half a hundredth of a point per decision or so. This is the strength the best human players in the world hold under pressure: a world-class human plays somewhere around PR 3 to 5 across a tournament, so this level sits at the top of that range and slightly above it.

Why a target, and why not every World Class member plays the same

Each of the twenty-five World Class members has a target PR of its own inside that band. The target is what that member is tuned to average over many matches — not a promise about the next one. Two things follow.

First, no two World Class members are the same player. One sits near 2.5, another near 3.5; one is a little sharper on the checkers, another a little looser with the cube. Each was given its own fixed sharpness within the level, so that meeting GG Jónsdóttir is not the same as meeting GG Van Damme.

Second, a single match will swing above and below the target, for a member exactly as it does for you. A match full of easy decisions produces a clean PR; a match full of close ones punishes everybody. The level holds as an average, and nothing is done to force one match into the band — no correction, no "making up for it" after a good game, no error budget being spent. That was tried in an earlier build and taken out, because people do not blunder on a schedule and neither should they.

How far from the top

The club's strongest player, GG Guru, plays the engine's best move every time: PR 0. A World Class member gives away around half a hundredth of a point on every decision that Guru does not. Over a match that gap tells — but it does not decide everything, because the dice still exist.

Put in rating terms: a World Class member starts at 2100, Guru at 2300. On the club's rating scale, that difference gives the World Class member an expected chance of winning of about 44 % in a single game, 40 % in a 3-point match, 37 % in a 5-point match and 35 % in a 7-point match. The longer the match, the less the dice can do for the weaker player. Those are the odds against the very top of the club; against members of the levels below, they turn around.

How a World Class member is tuned

The engine underneath every member is the same one: GNU Backgammon, which reads every position at full strength. A World Class member does not get a weaker engine. What changes is how the member looks at what the engine sees: through a little noise, so that when two plays are close, the wrong one can look right. How much noise, and how often the member is sharp rather than careless, is set for the level and then adjusted per member.

The settings were not guessed. They were fitted to how real people at this strength actually err — around 200,000 decisions by approximately 100 real players, from world class down to PR 15.9 — and then confirmed in engine-graded test matches before the level shipped, played by hand after that, and re-measured every time the cast changes — by the time the doors open, every level will have thousands of graded games behind it. When a World Class member plays like one, that is because the measurement said so, not because somebody thought it looked about right.

Where they go wrong — and where they don't

At this level "mistakes" is almost the wrong word. What the engine finds are differences of judgement in positions where strong players disagree — a play worth a few thousandths less than the best. Everything clear is clean, the ceiling on a single decision is very low, and a World Class member will not give you anything you did not earn.

The cube at World Class level

Checker play and cube handling are tuned separately, because in people they come apart. A World Class member's cube is nearly airtight: the doubles come when they should, the takes and passes are right at every score, and the remaining errors are the kind that only a rollout settles. Their cube decisions are fitted to how the strongest human players really handle it. You do not beat them with the cube; you survive it.

Is this your level?

If your PR sits around 3 and you have won things people have heard of, this is your level. For everybody else it is the level to test yourself against when you want to know exactly how far there is still to go — and the review will tell you, decision by decision.

Your own level is not a label you pick. When you start, the badge beside your name says provisional. As your career goes on it fills in with your average Level of Play, measured the same way the members are: play in the World Class range and you carry a World Class badge; play better, and it moves. Try one level below yours for pleasure, and one above it to learn.

Beat them, and they are yours

In Career Mode, beat a member in a tournament or a league and they are unlocked for good — on your account, across every career you ever start. From then on you can sit down with them for a friendly whenever you like, or just say hello. The twenty-five members below are the names on the trophies.