My grandfather used to say that novice chess players traded pieces for pieces, but strong players traded pieces for position. The masters, however, trade positions for positions.

The rules of chess are simple, you can teach them to a child in just a few minutes. There are different pieces which move in different ways, with just a few exceptions due to circumstances that are carefully defined. The equipment used in the game is simple, and the action is confined to a limited board space. There are never any surprises.

In spite of this, chess is a game of infinite subtlety and many levels, many of which are not obvious until the player has had years of experience and study. Below the rules there is the level of tactics,
how to produce certain combinations of moves and economies of action for both attack and defense, the students of the game memorize openings, gambits, and have identified tactical maneuvers such as forks, blocks, support, offense/defense, discovered checks, the concept of opposition, multiple attacks, and the necessity of using pieces in simultaneous roles. Below that level is the concept of strategy, such as dominating the center early in the game, the willingness to sacrifice pieces early to gain a stronger position, even when it gives no particular advantage at that point in the game, and the idea of development and the order in which pieces should be developed. And below that lies the level of intuition. Often a game is won because of decisions made early on for a totally different reason: strong players get lucky more often than weaker ones; and it happens often enough to not be coincidence.

The simple rules are the same for everyone, but advanced players also develop recognizeable personal styles which evolve over time. Students can read a game they do not know, played over a century ago, and make statements like "this was one by Capablanca, probably when he was a young man". There is nothing in the rules of the game that indicate why this should be so. The game has a history, and a great master of the past could not compete today because modern players have the advantage of understanding some of these deeper levels which was not common knowledge in the past. From a strict definition of basic rules has evolved a chaotic system which can only be adequately understood by non-analytic mental processes. Winning at chess has nothing to do with how many moves ahead you think, it is about that vague feeling that tells you to choose one strategy from a list of alternatives, a decision that will not pay off or fail until much later.

The point I'm getting at here is that even simple rule sets interact to form structures of unexpected complexity, systems sensitive to infinitesmal changes in initial conditions, what science calls chaotic systems. Chaos, of course, in the standad usage of the word, has nothing to do with it. Purely random systems, with no limiting rules or laws, don't seem to evolve into this kind of variety; on the contrary, they are usually quite predictable, if not in their specific states then in their overall characteristics. To develop truly complex structures, you need to start out with fairly restrictive rules, like the laws of physics.

There is no role for chance in chess, the only difference is who goes first, whether you are black or white. From then on, only the players matter. But there are also games where chance does play a role, such as poker and backgammon, where even the masters can lose to a novice, at least part of the time, depending upon the cards dealt or the throw of the dice. In nature, rigid rules interact with pure probability to create even more subtlety and complexity. The strict laws of physics also blend with the randomness of quantum theory to create our universe of infinite vaiety within finite constraints.

Why this should be so is a great mystery.