In my previous article on Darwinian Difficulty, there was a brief look, relating to Demon's Souls, at the concept of Subjective Difficulty. However, the concept of Subjective Difficulty is not restricted to brutally hard titles, and one of the most famous and accessible franchises of all time has been an example of this since 1996.
Before we continue, it's important to define two terms for the sake of this article:
Subjective Difficulty. Designing a challenge so that its severity is based on the player's skill level.
Safety Net. The degree to which the player can mess up and still succeed at the specific challenge.
Technically, we can argue that any challenge in a game is subjective by skill; someone who is a grand master at Street Fighter is not going to have the same problems with arcade mode as a player that has never touched a fighting game before. The key component in Subjective Difficulty, however, is that specific challenges are designed for different skill levels at the same time.
To achieve this, the player must have access to all (or most) of the available mechanics from the get-go. In order to design levels that allow different levels of skill to work, the player must have the option to use all the mechanics. If the levels are only designed around using one or two of the available mechanics, then it's not Subjective Difficulty, as both the novice and expert players are limited to the exact same thing.
With that said, there are a few considerations to understand about Subjective Difficulty. First is that unlocking mechanics as a form of progression is not considered Subjective Difficulty. If you have ever played a Metroid game, or the latest 2D Castlevania titles, there are always paths or sections along the main route that are blocked or inaccessible. As the player explores the game, they'll fight a boss or find a power-up that unlocks a new mechanic that can be used to enter the previously inaccessible area.
The point of contention is that it's not the player's fault that the area could not be reached, but the designer limiting the mechanics available. An expert player in Castlevania, no matter how good they are, will take the same path through the game as someone who is brand new.
Second is that the traditional use of difficulty levels is also not an example of Subjective Difficulty. Going back to the concept of the safety net, when the only difference between difficulty levels is stat-based (i.e., on "easy", enemies do less damage, but on "hard", enemies do more damage) then all the designer is doing is raising or lower the safety net based on the difficulty setting.
However, that doesn't mean that difficulty levels aren't a factor. God Hand for the PlayStation 2 has two forms of difficulty. At the start of the game, the player chooses a difficult level; this in turn affects the second layer. During play, at all times a meter in the bottom left of the screen displays the current difficulty level.
The difficulty of the game can fluctuate between Level 0 and Level Die (or 6) based on the player's performance. Taking significant damage or dying will lower the meter, which will drop the level down. The more the player avoids damage while continuing to make progress, the higher the level will rise.
The level of difficulty affects two things. First, it affects how aggressive the AI is. The lower the number, the less likely enemies will counterattack, attack in groups, or use their stronger attacks with the opposite more frequent at higher levels. The second detail is that at the higher levels (specifically Level Die) more (and more difficult) enemies will show up in the levels, forcing the player to adapt. Going back to the initial difficulty level at the start, the only things it determines is the starting level of the meter and how high it can go.
Playing God Hand, the game attempts to match the player's skill level by raising or lowering the difficulty. Both a novice player and a skilled player are going to take the same path through the level, but what a novice player will be facing will be different compared to someone who is consistently performing well.
Another form of Subjective Difficulty is providing different variations of the same challenge. Games like Tony Hawk's Project 8 or Banjo-Kazooie: Nuts & Bolts each feature challenges with basic, advanced and expert goals.
Every challenge in the games has a bare minimum to complete to get a bronze medal, which is the easiest way to finish it. There are also more difficult ways to attempt challenges, which could earn players a silver or gold medal. For example: in Project 8, completing a race while placing at least 5th would be a bronze award, placing 2nd gives silver, and placing 1st while finishing the race in under 2 minutes awards gold.
These harder considerations are always available to the player to try if they want and be awarded accordingly, but getting the bronze (or silver) award is good enough to check that challenge off as being "completed".
This system is also popular in many smartphone games. A variation on it in the popular Cut the Rope finds players striving to capture three stars in each level -- which are not essential for completion, but are necessary for completists.