I just returned home from a couple weeks out of town without much internet access. I've planned on continuing my series of blogs on playing to win at games that do not warrant a hyper-competitive attitude, including an entry on Slender TEP and an entry on puzzle league games. But in the process of writing the puzzle league blog, I realized that many of my comments belonged in a separate blog about puzzle games in general, which could then be referenced in the blog more focused on puzzle league strategy specifically. Apologies that this blog does not have the usual subtitles, pictures, and captions to break up text, but I didn't think this was a blog that warranted those measures.
Puzzle games are, at their heart, composed of three things: an arrangement of elements, a mode of player manipulation of those elements, and a goal. Without the first, there's nothing to manipulate, so gameplay is impossible. Without the second, the player can only watch the puzzle sit there, with no means of achieving the goal. And without the third, there's nothing to make one decision preferable over another, so gameplay is arbitrary and uninteresting. This last ingredient is negotiable, since one can imagine an "open world" puzzle game with no explicit goal set (for example, the World of Goo Corporation area in World of Goo, where the player can arrange goo structures freely without a win condition), but the first two are absolutely necessary.
In these terms, a puzzle game remains interesting by rearranging the elements, while keeping the mode of interaction and the goal the same (sometimes the mode of interaction is modified, too, but usually only when new modes of interaction are added one at a time to introduce the player to the game more slowly). Each new level has a different set of elements to be manipulated, so even though the mode of interaction is the same, a different strategy must be employed. This means a good puzzle game must have strategy which is contingent on the particular arrangement of the elements. If the same strategy can be employed effectively in every situation – that is, if the strategy is not contingent – then strategic diversity is inhibited, and strategic diversity is the heart of what makes any strategy game interesting, puzzle games included.
Consider the classic puzzle genre: the elements are differently colored blocks, arranged in a two-dimensional grid on screen. The mode of interaction is through the swapping of adjacent blocks. The goal is matching three or more like-colored blocks in a line to clear them. This premise is common in puzzle games, but it has an essential problem: by a series of horizontal and vertical swaps, you can move any block anywhere on screen, so the initial arrangement of blocks is largely arbitrary since you can rearrange them as freely as you please. Strategy is not contingent on the arrangement of the elements, so strategic diversity suffers.
Bejeweled solves this problem by restricting legal swaps to those that create a match of three or more. This restricts player interaction really quite heavily; at any given time the player likely has under ten possible moves, and often times only two or three. That means strategy is quite contingent, since your decision-making must change depending on how the elements are arranged; but strategic diversity is still fairly low, simply because there are so few options at any given time.
Puzzle league, on the other hand, introduces a different restriction: swaps can be made freely, but only between horizontally adjacent blocks. This means that players can control the column of a block, but not the row (at least, not directly). Player options are still fairly numerous – in a 6x10 grid, there are 50 possible moves at any given time, compared to 104 possible moves with vertical swaps allowed. But by restricting vertical swaps, strategy is contingent on the blocks' arrangements, so strategic diversity is actually increased by reducing player options.
If you've played both puzzle league and Bejeweled, the difference is pretty evident. Bejeweled is generally considered a fairly casual, laid-back game, with fairly little strategic decision-making; puzzle league has remarkable depth of strategy, and a player can easily invest dozens or even hundreds of hours without hitting a skill cap.
Conclusions
One conclusion of all this is that puzzle league games are better than Bejeweled – and I'm certainly friendly to that proposition. But more generally, I'd argue that in designing a puzzle game (or even other strategy games) to maximize strategic diversity, the player must have enough freedom to have many decision options at any given time, but with too much freedom, player strategies do not need to adjust to a given situation, and strategic diversity suffers again.
So, at least in these terms, the trick is to find a set of restrictions that forces the player to come up with different strategies tailored to particular situations, while retaining player options as much as possible. In the case of match-three block puzzles, that means placing the smallest restriction on player interaction possible that still forces the player to consider the blocks and choose a strategy based on them, rather than form a strategy beforehand and then force the blocks to conform.