I think we need an easier way of gauging the difficulty of our own levels. Maybe something like this helps:
Obviously, this graph was done very quickly and is by no means representative of all possible levels. However, it can be a useful indicator of where your level
probably is on the difficulty scale.
In the above example, if the level provides 5 skills in total, and all 5 are required in the intended solution, then it's likely to be a "Medium" difficulty level (or possibly higher).
However, if there are 35 skills in total, and only 1 is required, it's likely to be a "Beginner" level.
Again,
this graph does not suit all levels. Levels which give red herring skills or skills which are of absolutely no use in completing the level are obvious anomalies, as are levels which may only require a small number (<5) of skills, but for which the solution is extremely obscure. In these cases, however, the creator is likely to be more aware of how difficult their level is.
I'd suggest taking a look at your level: if it has a total of 10 or more skills,
all of which must be used in a very particular way, it's likely to be quite a hard level. 5 or more, and it's likely to be Medium difficulty.
Comments, suggestions, agreements, elaborations?
EDIT: Perhaps "necessary" assignments must be further defined as "non-trivial". So, a gap requiring 15 Builders to get across when the level only provides 15 Builders is obviously not a "Hard" level, but the assignments are trivial, so the graph no longer applies in quite the same way. Such cases must see the gap as "1 obstacle requiring N of the same skill, with N being equal to the number of that skill which is provided", redefined as 1:1 for the purposes of this graph.
EDIT 2: It occurs to me that I could be equating difficulty with lack of open-endedness. I do genuinely think that the minute a level requires a particular skillset, and only provides
that exact skillset, it becomes a difficult level.
Oh No! More Lemmings (from Wild onwards) is a very difficult pack for anyone who has never played it before, and most custom levels are even harder.
I think what's happening is that the community are brushing open-ended levels away as "trivial" or "beginner", and only gauging the relative difficulty of the remaining puzzle levels, starting with "Easy" as something which the creator would expect most people to be able to solve. This seems problematic, but I can't quite put my finger on why.