What makes a game difficult? What makes a game challenging? What makes a game frustrating?
I'm sure if you asked a hundred people, they'd give you a hundred different answers. Difficulty, challenge and frustration depend on individual experience, and expectation.
The key to thinking about this is not to consider what you personally find difficult, but rather to consider that not all people are created equal, and therefore tasks that might seem trivial to one can be frustrating to another. It is then important to consider that a game developer can only draw from their own knowledge and experience, and that they will always have to make choices about how they create the challenges in their game.
I write this now, because of the trend over the last few years to describe difficult games in terms of Dark Souls, and the complimentary trend in which others take umbrage at the comparison. Games are like Dark Souls because they're difficult, but Dark Souls isn't difficult! Games are like Dark Souls because of these mechanics, but those mechanics aren't key to Dark Souls!
Honestly, it's comparable to the endless discussions about what makes a Rogue-like, Rogue-lite or whatever. And who wants to die on that hill?
I've also seen a few interesting thoughts from others about difficulty that has made me think about my own opinions on the matter. Firstly there was Shamus Young in the middle of discussing the Arkham games, then there was Philippa Warr discussing the difference between difficulty modes in Thimbleweed Park, and finally a short video on Hyper Light Drifter by Matt Lees.
I can't remember the first game I played that had a difficulty choice at the start. But this option has become far more popular over the years. A lot of games used to just drop you in at the beginning, with the game ahead a complete unknown.
Difficulty choices can make a game more accessible, and they can add extra challenge for experienced players. There's also a range of different ways in which a game can be made more or less difficult, depending on the game in question.
There is no game for which alternative difficulty modes could not be created, but creating these choices can vary in difficulty. I'd like to see all games offer players a choice of difficulty, but there may be limits to what the developers wish to (or can) create.
There's two ways to offer players a difficulty choice: Present them with options at the start of the game (which may or may not be alterable throughout the game), or incorporate the difficulty choice within the game itself (or indeed use a combination of both). There are so many great examples of both methods (and terrible examples) that I couldn't possibly mention them all, but I'll try and be as comprehensive as possible.
The starting option is often what people consider when they think of difficulty modes. You get a choice between different levels of difficulty at the start of the game, with very little context for that choice. Most players will probably choose the "normal" difficulty, or whichever is pre-selected as standard. "Easy" difficulty might seem like a cop-out, especially if you have no idea what it actually entails. "Hard" likewise might seem too daunting.
The more options there are available, the more confusing it's likely to be for a new player. It's more forgiving when the game is likely to be replayed multiple times, as the player can start at a lower difficulty and then on repeat playthroughs ramp things up to increase the challenge. Sometimes the difficulty can be adjusted mid-way through, so if you've made a poor choice there's the option to recover without having to start from scratch.
Common examples of this are Wolfenstein, Doom and Quake. The tiers of difficulty in such games generally alter relatively easily modified elements of a game. These might include the amount of health a player has, how much damage the enemies do, how much damage the player can do, and so on. They also might be more complex, and involve enemy types and enemy placement.
The two examples I've picked are System Shock and Mount & Blade. They both offer very different ideas on difficulty. System Shock gives the player a series of options for difficulty, with four sections. "Combat" governs the enemy strength, "Mission" governs certain story elements, "Puzzle" which governs certain interactions like hacking keypads, and "Cyberspace" which was a separate section of the game. This allowed players to adjust the game to their needs, especially necessary due to the rather awkward control system and user interface.
Mount & Blade has a different set of difficulty options, more relevant to the sort of game that it is. It allows you to change the amount of damage that you receive, how smart the combat and campaign AI is, and various other minor options. These options are welcome, but not exhaustive. There are a vast amount of other options that could have been adjustable, but are not (such as how much money and reputation you receive or lose in certain situations). The in-game difficulty can be altered at almost any time, allowing you to tailor your experience to make it as challenging as you like.
Both games show flexibility in their approach, in different ways. System Shock's options allow you to affect the very mechanics of the game, for example setting "Combat" to "0" will make enemies virtually unresponsive and easy to defeat. Mount & Blade doesn't offer options to significantly change the mechanics, but rather allows the player to reduce the effectiveness of the non-player characters. Mount & Blade also doesn't allow the player to completely lose the game, at most you'll only lose your army, your money and some items, but you live to fight another day.
Point & Click adventure games usually don't offer difficulty options, mainly due to the extra work required to adjust puzzles. There are plenty of adventure games in which the puzzles chain together in such a way that to take out an item, character or interaction would affect so many other parts of the game. There are a few good examples though, such as Monkey Island 2. While I wouldn't consider MI2 to be a difficult game, there are a lot of challenging puzzles which newer players might find frustrating or incomprehensible. Long-term adventure game players can sometimes feel like certain puzzles are easy due to the experience that comes with having played many games of a certain type.
The easier mode in Monkey Island 2 alters the solutions for several of the more difficult puzzles, usually replacing it with alternative dialogue, removing items or interactions from a puzzle chain, or just omitting or changing a scene entirely. You get a slightly different experience, and miss out on a few jokes, but otherwise the majority of the game and story are the same.
Of course as a developer, you might decide that you can't or don't want to offer a difficulty choice at the start of the game. In this case, you either give every player the same experience, which some players will find easy, others too hard. A good example for this is something like Devil Daggers, an arcade-style experience where the goal is to last as long as you can against ever more intense swarms of enemies. Difficulty options could be added, but the developers decided that they wanted all players to face the same challenge, with a leaderboard to show who can survive the longest. This is comparable to many earlier games, which at best would have hints and tips for you in the manual, but would otherwise expect you to deal with a single, standard, one-size-fits-all, difficulty.
Then you have examples from adventure gaming such as King's Quest and Quest for Glory. Both of these games don't allow for a difficulty choice at the start of the game, but they offer potentially different experiences to different players. In King's Quest, you were tasked with regaining the three lost treasures of the kingdom. How you go about this task is up to you, and while many of the puzzles had a single solution, others had two. Usually the choice was between a peaceful and a violent solution or bypassing the puzzle by forfeiting an item of value. Solving the puzzles in the more peaceful and usually more difficult method would gain you more points, so it rewarded players for playing the game as the developers intended, while still allowing other players to complete the game in a less optimal way if they couldn't solve the puzzles.
Quest for Glory, with its merger of RPG and adventure gaming genres, allows the player to select from three character classes, each of which gives you a different potential set of options for solving puzzles. The Fighter generally prefers brute force, the Magic User uses spells, and the Thief uses subterfuge. Many puzzles allow for three different solutions, and often the player is able to use a different solution than their chosen character class, if they have the prerequisites for it. For example, a Fighter may break open a locked door, while a thief picks the lock, and a magic user uses an unlocking spell. But if my magic user has a high enough strength, then they are able to break open the door. This sometimes made the game easy, but no less enjoyable.
So with those examples out of the way let me turn back to Dark Souls. The Dark Souls games are beloved by their fans, and have had endless gushing praise about them, for good reason. They provide an experience that is similar in many ways to other games, but different enough to stand well apart. They have done enough to carve their own niche, and have been popular enough that others are starting to copy them.
They don't offer a difficulty choice at the start. But they do offer choices, many of which will affect the difficulty, especially early in the game, and especially for a new player. As an RPG, you choose your character class, and you have a small choice of starting equipment. These choices can have a big impact on how difficult the early game is, with the different character classes having wildly varied starting equipment. The Knight, for example, has a great armour set and weapon, whereas the Deprived starts with nothing but a club and wooden shield. You also get an item selection, most of which is of minor use.
Dark Souls handles difficulty in a similar way to Quest for Glory, there are player-made choices in terms of your character class which affect how you will approach different situations. There are also choices in terms of your equipment and and how you spend your upgrades throughout the course of the game. Some choices can make things easier, and some choices will make things harder. Part of Dark Souls' mystique is that it doesn't readily explain the consequences of your choices. You may make valid choices for the stage or area of the game that you're currently having problems with, but correcting poor choices can be difficult or impossible.
So even though the game is carefully designed, and it provides the same choices for all players, the difficulty you will face is entirely dependant on player choice and player ability. The experience is different for all players, because the choices and ability of all players will be different. What might feel fair and balanced to one player will feel frustrating and difficult to another. What provides a challenge and excitement to one, provides a brick wall and disappointment to another.
I've seen many suggest that the difficulty is part of the game, that the oppressiveness is ingrained into the story and to make it easier is to ruin this. However, there are players who will be more skilled and find the game easy anyway, and players who will find the game unbelievably hard without ever getting to experience enough of the story for this to have any beneficial effect. Not to mention that the game has been altered since release, with patches making at least a couple of changes to make things easier.
Difficulty is always a choice, from the way the game is designed, to the ways in which it is played. I have no issue with a game being made deliberately more difficult, or being given a dozen different difficulty options so that I can experience the game as I see fit. What I want people to understand is that the knowledge, experience and skill levels of players is a wide range, and that allowing flexibility in difficulty will allow a greater number of players to experience your game.