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.