system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did game manufacturers of tabletop games ensure that at the opening of the game, theres equal probability of every player winning ?

the most prominent example is chess which has had the same rules (including quirky rules like en passent) for more than a century. And those rules stand the test of time in that even the best computer engine evaluates most starting moves to be about equal. I also played a game called splendor which has multiple winning tactics but it seems like each tactic has equal pros and cons. I am speculating that now there are brute force methods devised so that a computer plays the game over and over again and changes certain modifiers and stats until the game is equal for each player. The game would then be released with those modifiers. But I wonder; how did game making tacticians of the past who did not have access to such complex computer programs, ensure that in a game that has a million possible moves, there is equal probability of any player winning with the best play ?
gpt
Short answer: they don't.  For most games, it's *not* known that there's equal probability of winning with perfect play.  For some popular games, actual *perfect* play guarantees that one player or the other will win - Connect 4 is simpler than chess, but a prominent example of a game where perfect play *always* allows the first player to force a win.  Yet we're collectively still willing to play it, because most people don't know how to play perfectly, and of those who do a reasonable proportion might still make a mistake.

However, game-makers generally have a reasonably good idea that within the bounds of human play, each player has a decent chance of winning, simply because they've playtested the game and had others do the same for several iterations prior to release, and taken the time to patch any obvious discrepancies that may have arisen.  They'll have taken a variety of test-players and tweaked the rules until they got roughly even outcomes.  They can, and do, still miss things, but these things tend to be relatively buried in the rules.

For games like chess, it's a similar situation, only there was no single "game-maker" and no "release", so the rules were adjusted by the players "on the fly" to keep the game even enough to be interesting.  Before the establishment of governing bodies for some of these games, the rules might have differed depending where you played.