Complex is being used in a different context here though. You are meaning complex as in strategic complexity. The parent (I think) is using it in terms of the games rules. Go is pretty simple in principle: place stones on the board one at a time, and remove enemy pieces completely surrounded by your own. But it's fairly complex to know what exactly constitutes being surrounded. Chess has 6 different kinds of pieces that have different movements, and different kinds of rules depending on the state, and promotion at the end, castling, and en passant. Checkers is a much simpler game because there's only 2 kinds of pieces, and 2 kinds of moves. Strategically, Chess isn't leaps and bounds more complex than Checkers since Carlsen has an Elo rating of 2800 in Chess, and Tinsley had an Elo rating of 2700 in Checkers and I believe it's the same deviation of 200.

Checkers has adjusted its Elo system over time. I believe that it now matches chess except with a floor of a 1000 rating. From http://icheckers.net/ratings/, the current ratings range goes from 1000 to 2297 among active players, and up to 2510 among inactive players.

Even if you use the larger range of inactive players, that's a range of 7.5 times the standard deviation. Which is considerably less than chess.

Tinsley isn't on that list, and I saw it claimed that his rating was 2700: https://en.wikipedia.org/wiki/Marion_Tinsley

Chess has a floor of 1200 for novices. So I'm not sure your point.

The Elo system for Checkers has changed over time. Tinsley had a rating around 2700, but he would not get that rating today.

Chess ratings from the USCF have a floor of 100. What you are thinking of is that they start people at a provisional rating of 1200 and then let them drift to where they belong. But a person who just knows how the pieces move will quickly head down towards that floor.

Know of any resources that help figure out what the Elo SD of a particular game is, and the range? Also, know of anything written about various ways of measuring the complexity of a game? I'd never thought about the number of SDs thing.

By this measure, is there a more complex game than Go, but which is not as widely played?

(Question from someone who does not know anything about board games.)

I ask because a natural question arises: can one engineer a game specifically so that it is extremely difficult for a machine to master compared to a human -- due to some strategic complexity, or some approach that does not lend itself well for current AI models.

edit: looks like there's at least one http://arimaa.com/arimaa/

Probably not.

Even if a game was more potentially complex than Go, it would be hard to establish the dynamic range of Elo ratings unless a lot of people played it, and hard for skill variation to be that high unless a lot of people studied very hard to become very good at it.

Yeah, "deep" is probably a better term than "complex" to describe Go.