I've gone to hell and back (like, literally. It's full of lava and machinery down there). As Silent Hill: Homecoming's war-weathered Alex Shepherd, I have defeated all manner of enemies, from run-of-the-mill scythe-headed fleshbags to the monstrous, porcelain-doll reincarnation of a murdered child. I have survived everything this labyrinthine horror of a town has built around me - a crumbling hotel, stinking sewers, and a graveyard teeming with ravenous, skinless dogs. I have finally found my way back home, where I am to discover the gruesome secret my family has kept for generations - the reason for my younger brother's disappearance and the town's rapid decline into disrepair.
After all I have been through, however - after all the terrors I've endured and the monsters I've barely escaped - I am finally defeated by what lies behind the attic door. It is no monster. It is something much, much worse.
The key to the Shepherd family secret is a sliding puzzle.
After twenty minutes of this exercise in frustration, any semblance of immersion I may have felt has dissipated, fog turned to a cold, hard rain. I turn on the lights, scrambling for a walkthrough. Alex Shepherd and I are no longer a resilient team of grim and steely determination. He is merely my avatar, a somewhat grumpy mess of pixels - and I am the player, suddenly reminded of why I chose videogames over my plastic sliding puzzles as a child.
Traditionally, puzzles are a game in themselves - a test of one's cleverness, used as a defined distraction from the more tedious aspects of life. A good puzzle encourages its player to think differently, and rewards him upon its completion. A good puzzle should not rely on luck or random chance, and conversely, it should not have to rely on a specific area of knowledge to be solved (a puzzle that relies on mathematical knowledge, after all, is little more than an equation). A good puzzle aims to be interesting while avoiding contrived difficulty, does not aim to frustrate its player, and may be as easily solved by a child as by a fully-grown adult.
So how do puzzles set in the context of a videogame differ? While the term "puzzle" may be increasingly applied to obstacles in games that may once have not been considered puzzles at all, it's important to recognize the origins of the puzzles we find in games today. Videogames exist in a different space, and it's only natural that puzzles have evolved to fit that space.
This is why we have jumping puzzles, inventory puzzles, and the ubiquitous crate-pushing puzzles. As an obstacle to overcome, and as a break from the more action-oriented parts of a videogame, these obstacles still adhere to the traditional definition of a puzzle, but having grown far from their original, standalone form into a virtual world, they have far transcended their origins.
Puzzles' shift into videogames represents their shift into a narrative-based art form; when cleverly used and contextually appropriate, a puzzle can be integral to strengthening a game's story and the player's experience of it. It's something that makes puzzling in videogames special, and isn't something you're likely to find in your newspaper's daily sudoku puzzle.