I love simple games, so it couldn't come as a surprise that I'll spend a night or two obsessing over Sudoku here and there (I currently struggle through the "hard" level).
***Dave, with the comment "Ho Hum" passed along an article about Sudoku that lays out basic rules for completing a puzzle.
The basic rules in the article cover easy puzzles and about 90% of medium puzzles, but won't give you the method for solving hard puzzles (I haven't played any "evil" puzzles yet.) The article puts across that all you need to do is follow some simple rules, but that isn't true any more than saying "all you need to do to play chess is to follow some simple rules." While it's true that a few simple rules will solve many instances of a game, for harder instances, all the simple rules will do is take you to a point where complex rules can be applied more easily.
For example, something that the article doesn't mention is that if two numbers in a given group can each occupy only one of two spaces (and the spaces are shared by both numbers), no other number can occupy that space. It's not a rule; it's logic. The more difficult a puzzle is, the more likely you're going to encounter a situation where you have to reason out a logical tool that you've never encountered before. Some people don't care for it, but I find it a real pleasure.
Most games have a few simple rules that can be followed to quickly put the player at an average level, able to easily beat a novice. Mastery requires going beyond a few simple rules; if all it took was a few simple rules, everyone would be a master. To reduce a game's strategy to a few rules reduces the fascination of a game to the company of the people one plays with, and, in that case, you might as well do something other than play games.
I love the catastrophic element of game strategy: one strategy works just fine until some unanticipated boundary is crossed, and then all hell breaks loose.
Oh, no! The Tetris blocks just keep coming faster and faster...!