Fan based content
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Difficulty is a system on Candy Crush Saga Wiki to measure how difficult a level or episode is. This system was introduced in 2013 and is inspirational to many other game wikis (especially King games).
Table of all Reality levels by difficulty (Note: large page size)
Table of Difficulty Distributions and Episode Averages
Contents
Difficulty code usage
There are 12 types of difficulty, ten of them sequential, two of them peculiar. They are:
0  None (white)  
1  Very easy (cyan)  
2  Easy (teal)  
3  Somewhat easy (green)  
4  Medium (yellow)  
5  Somewhat hard (orange)  
6  Hard (red)  
7  Very hard (maroon)  
8  Extremely hard (black)  
9  Nearly impossible (navy)  
V  Variable (purple)  
?  Impossible (gray) 
Episode means
An important thing that comes with level ratings is episode means, the indicator of how hard each episode is on a scale of 0 to 9. The overall difficulty of the episode is also determined with it.
Calculating episode means
To calculate the mean of each episode, we must first remember how to convert each difficulty level into its given number (Noted above, in the "Difficulty code usage" section. It's different for variable levels, explained below). The higher the difficulty, the higher its number.
The difficulty of a level can be determined by taking a large random sample of players who completed the level and taking a sample mean. A large sample is necessary to minimize the effects of fluctuation errors due to lucky players, as smaller samples have large variability. Sometimes a player will get stuck on an "easy" or "medium" level, and sometimes a player will beat an "extremely hard" level on their first attempt.
Then, we must add up the 15 (Usually) numbers (in other words, calculate the sum of the 15 numbers) and we must divide the number we'll get by 15 (Usually). The final number we'll get, which is rounded to the hundredth decimal place, is the arithmetic mean of that episode. (Note: In the first two episodes, we must divide the sum by 10 instead of the usual 15).
NOTABLE EXCEPTION: Variable levels. If an episode contains variable levels, we must subtract the number of variable levels from the size of the population (Aka the number we have to divide by during the final operation). Variable levels are also not included in the sum that we have to divide to calculate the episode mean, as if the episode has <15 levels.
Impossible levels If an episode contains an impossible level, the difficulty of the episode is also impossible and the mean cannot be calculated, the episode has an undefined value.
Undetermined levels. If an episode has more than 5 undetermined levels, the episode itself has an undetermined difficulty.
Translating the mean of the episode to the overall difficulty. The names of the episode difficulties are identical to those used for level difficulties. Each episode difficulty has its own cutoffs ("Borders"), which is noted below, in the "Usage criteria and examples" section. Note that if the mean is lesser than the cutoff mean by 0.01 to 0.1, the episode is considered to have split difficulties (For example, if the cutoff is 6, an episode with a mean of 5.9 to 5.99 has split difficulties).
Examples
Example 1: An episode has 4 somewhat easy levels, 8 somewhat hard levels and 3 hard levels.
Remember, the number assigned to each somewhat easy level is 3, the number assigned to each somewhat hard level is 5 and the number assigned to each hard level is 6.
1. Calculation of the sum: 3+3+3+3+5+5+5+5+5+5+5+5+6+6+6 = 70
Or (3x4)+(5x8)+(6x3) = 70
2. Division: 70/15 = 4.(6) ≈ 4.67
The mean of the episode is 4.67
Example 2: An episode has 2 very easy levels, 6 medium levels, 5 extremely hard levels and 2 variable levels.
Remember, the number assigned to each very easy levels is 1, the number assigned to each medium level is 4, the number assigned to each extremely hard level is 8 and variable levels are not assigned any number.
1. Calculation of the sum: 1+1+4+4+4+4+4+4+8+8+8+8+8 = 66
Or (1x2)+(6x4)+(8x5) = 66
2. Division: Remember, the episode has two variable levels. Therefore, we must divide 66 by 13 instead of 15.
66/13 ≈ 5.08
The mean of the episode is 5.08
Comparing episode means
 If the difference between the means of two episodes is 0, we say that they are of the same difficulty / one episode is of the same difficulty as the other.
 If the difference between the means of two episodes is at least 0.01 and at most 0.09, we say that they are of similar difficulty / one episode is of similar difficulty to the other.
 If the difference between the means of two episodes is at least 0.1 and at most 0.19, we say that one episode is slightly easier/harder than the other.
 If the difference between the means of two episodes is at least 0.2 and at most 0.49, we say that one episode is easier/harder than the other.
 If the difference between the means of two episodes is at least 0.5, we say that one episode is much easier/harder than the other.
 Note that 0.5 in the last bullet point is a debatable number and may change.
More examples
 Episode N1 has a mean of 4.93, episode N2 has a mean of 5.02. Therefore, N2 is of similar difficulty to N1.
 Episode N3 has a mean of 3.83, episode N4 has a mean of 4.93. Therefore, N4 is much harder than N3.
 Episode N5 has a mean of 6.27, episode N6 has a mean of 6.53. Therefore, N6 is harder than N5.
 Episode N7 has a mean of 7, episode N8 also has a mean of 7. Therefore, N8 is of the same difficulty as N7.
Notes for convenience
 If the sum has to be divided by n, adding or subtracting a number from the sum changes the mean by 1/n.
 If n=15, the mean changes by 0.0(6).
 Better numbers for this case exclusively  adding/subtracting 3 numbers specifically changes the mean by 0.2.
 If n=14, the mean changes by 0.0(714285).
 If n=13, the mean changes by 0.(076923).
 If n=12, the mean changes by 0.08(3).
 If n=15, the mean changes by 0.0(6).
 Length between cutoffs:
 2 for very easy and nearly impossible.
 1 for easy, very hard and extremely hard.
 0 for none (Unused episode difficulty).
 0.5 for the rest.
Usage criteria and examples
Grading  Description  Concrete examples  

None 

*Exclusive to a few levels*
 
Very easy (Episode means of 1–1.99) 

*Rare Difficulty Level in High Episodes*
 
Easy (Episode means of 2–2.99) 

*Uncommon Difficulty Level in High Episodes*
 
Somewhat easy (Episode means of 3.0–3.49) 

*Usually Common Difficulty Level*
 
Medium (Episode means of 3.5–3.99) 

*Common Difficulty Level*  
Somewhat hard (Episode means of 4.0–4.49) 

*Common Difficulty Level*  
Hard (Episode means of 4.5–4.99) 

*Common Difficulty Level*  
Very hard (Episode means of 5.0–5.99) 

*Common Difficulty Level Especially in High Episodes*
 
Extremely hard (Episode means of 6.0–6.99) 

*Rare Difficulty Level in the Earlier Levels, but Very Common in the Later Levels*
 
Nearly impossible (Episode means of 7.0 and above) 

*Uncommon Difficulty Levels, often nerfed. Some levels don’t even get redesigned!*
 
Variable 

*Very Rare Difficulty Level*
 
Impossible 

*Extremely rare difficulty level*

Amendments to difficulty scales
There are two notable changes to the difficulty nomenclature throughout CCSW history.
2016 Difficulty Syatem change
Since 2016, there were additions to the difficulty system:
Key Points
 The "Nearly Impossible" difficulty was introduced as the new top difficulty, above "Insanely Hard". This applies to levels which are almost unbeatable without the use of boosters.
 The "Insanely Hard" difficulty was renamed to "Extremely Hard". This is the secondhighest difficulty, below "Nearly Impossible" but above "Very Hard".
 Levels originally are "Insanely Hard" were changed to "Nearly Impossible", unless the level does not receive 70% votes for "Insanely Hard" ("Nearly Impossible"), which will result in an instant downgrade to "Extremely Hard".
Change map
The following tables illustrate the colour codes and changes for each difficulty rating.
 The first column shows the new colour codes, ie. those currently in effect.
 The second column tells you whether/how this difficulty colour was changed.
 The last column shows the old colour codes.
New Colours  change  Old Colours  




Color change
Effective August 7th, 2015, the difficulty colour coding in the wiki was changed. The new colour codes used were thought to be more intuitive, as they form a gradual progression through the colour spectrum from light and cyan to dark and red.
Key points
 The new colour for hard (red) was previously used for very hard.
 The new colour for very hard (maroon) was previously used for impossible.
 No colour coding is added to levels whose difficulty is undetermined.
Change map
The following tables illustrate the colour codes and changes for each difficulty rating.
 The first column shows the new colour codes, ie. those currently in effect.
 The second column tells you whether/how this difficulty colour was changed.
 The last column shows the old colour codes.
New Colours  change  Old Colours  




Trivia
 The system originated from the List of Levels, in which the difficulty of levels were once graded as "considerably hard for some", "considerably hard", "hard", and "extremely hard".
 No one knows who actually created the difficulty system.
 The colour for "Medium" was once between blue and purple, but since the colour was too similar to purple, it was then changed to the colour salmon. Currently, the colour of medium is gold.
 This was also the case with the colour for "Variable", which was formerly yellow. It was then changed to green to make it easier to see on a white background. Currently, the colour for variable is purple.
 It also happened with "Impossible". The former colour of impossible was white (it was specially designed for April Fools). However, once this difficulty was officially implemented, for the the glitched version of 578, it was changed to dark red. Currently, the colour for impossible is gray.
 Before, there was no "Impossible" difficulty. It was first given to level 1 as an April Fools Joke, represented by the colour white.
 In the same year all very easy levels were reassigned "extremely hard" and the rest of the levels were reassigned "very easy".
 When level 578 was found out to be impossible without jelly fish, the impossible difficulty was still white.
 Level 276 of Dreamworld was once given the impossible rating. It was downgraded since it was still theoretically possible to be completed.
 The first "very hard" level was level 30, but it got downgraded afterwards. The first one currently is level 197.
 The first "extremely hard" level was level 35, but then it got downgraded and then redesigned. The first one currently is 741.
 The hardest levels (and impossible levels) in the game have shifted throughout the process of making this game.
 First having level 35, then moving on to 65, considered by majority to be the hardest level.
 After that, the infamous 147 was released. Being the first ever nearly impossible level, maintained to be the hardest level in 2013. Its Dreamworld counterpart was also the hardest in its realm until they were both nerfed.
 Then, 350 was released and took over 147.
 With the nerf of several hard levels on May 28, 2014, 578 became the hardest level in the game, and initially it was even impossible without using boosters.
 With the nerf of level 578, early versions of 276 Dreamworld became the hardest since getting 300 blue candies with limited moves and blockers was an excruciatingly difficult job, almost impossible.
 Level 276 of Dreamworld received a nerf in June 2014 and (possibly) the hardest level in the game became 289 Dreamworld.
 When 380 Dreamworld was released, it was impossible without boosters, like 578 in reality.
 With the nerf of 380 Dreamworld shortly after its release, 289 Dreamworld again became (arguably) the hardest level before being taken over in September 2014 by 677, because, like 276 Dreamworld, it was almost impossible without boosters.
 677 was nerfed in October 2014. Later that month, 735 was released and arguably became the hardest level in the game before being nerfed in November 2014. 289 Dreamworld was once again considered the hardest level after both of said nerfs.
 829 was released in January 2015 and became the hardest level in the game before being nerfed the following month.
 After a yet another reign of level 289/Dreamworld, it was taken over by 1330 in January 2016.
 On October 20, 2016, 2069 was released. It was considered the hardest level due to its incredibly low amount of moves.
 2069 was arguably taken over by 2741 in August 2017, also due to its insanely low number of moves.
 The definition of "the hardest level in the game" is subjective to every player. Arguably, the "hardest" level in the game is 3599, due to its insanely low amount of moves to collect 100 orders.
 King marks these levels as "super hard" or "nightmarishly hard" in the game.
 In Dreamworld, more extremely hard levels were released alongside challenging episodes starting with Funky Fortress, which continued until the end of the realm (expect a few episodes in between). Later episodes of Reality also contain tons of extremely hard levels.
 It is theorized that the recent "surge" of impossible levels is because of oversights caused by the increased release rate of episodes.
 Notable formerly impossible levels include: 1949, 2598, 3348, 3455, 3615, 4550, 5344 and 6196.
 The number of attempts for a specific player may not always represent the overall difficulty of the level as the player can get lucky.