As a creator, how do you decide on the optimal difficulty of your design?

I don't think it is possible to be completely unbiased when reviewing your own work. You are simultaneously your own harshest critic and your most loyal defender. Levels will always be easier for the creator than for the player, assuming the player doesn't find any shortcuts, but that is neither here nor there.

I do, however, believe the objective criteria you set forth are very good indicators of the difficulty of any particular step in the level, and a level is as hard as is its hardest step. I approach many things with the philosophy that every problem can be broken down into smaller problems to be solved one at a time, and Mekorama is no different. Every good level is essentially broken down into several tiny puzzles that have to be solved in order to accomplish some goal. These may be skill based, logic based, or pure luck based. The hardest step in the puzzle is the ultimate difficulty of the entire level, since anyone capable of solving that step, will most likely be able to solve the other steps quite handily. I always aim for the hardest step to be either the last step or the next to last step. (I rarely achieve this so don’t go looking for it in my levels lol.) I feel if the hardest step is first, and the player takes a while to solve it, but the rest of the steps are easy, then the level is pretty anticlimactic. On the flip side, if there are lots of steps, and the last step is the hardest, AND the involves some risk of “death” either by electrocution or falling off the edge, then the level can be tedious as the player has to redo all the easier steps leading up to the final one. I do like having a period at the end after the player has solved the hard part, but before they win, when they can appreciate that they have just beaten the level. It’s not always possible, but I think it is a nice psychological boost in the level’s appeal.

I’m sure everyone knows I don’t really aim to make difficult levels. I imagine some levels are difficult in places I didn’t expect, but I really aim to just have a nicely paced puzzle, with time to breathe in between steps, and not a lot of luck involved. Those are the types of levels I enjoy playing, so that is what I make. I feel the difficulty level is not as important as good pacing and the “fun element”. There are lots of excellent levels on here that are incredibly easy, and there are lots of garbage levels on here that are hard, or vice versa.


TLDR: I ramble a lot. Something about steps. Psychology. “Fun element”

 

It's a tough question. Luckily I got some ideas after seeing @sawdust 's reply. I think deciding the best difficulty of own level as a creator, is like deciding the best amount of sauce for the customers as a cook=P.

When there is a time which the creator find his own level easy but the players find them hard. Mostly because of two reasons I guess. Inconsistency or "unknown"(not sure is it the proper word for that, please let me know if it's correct or not, sorry for my eng) . For inconsistency, it is like, let' say, when the creator find the mechanism works consistently while the players don't. Which means some possible errors are not discovered by the creator while testing it, so the players are facing troubles which the creator have never face before.
For "unknown", which is quite common I think from lots of levels out there somewhere, it means there is something in a level the player would never have a clue except for the one who made it. Something that in the level has to be figured out but it is beyond logic. The only way the player could find that out maybe only through trial and error, which the creators didn't have to experience it as they know their design.
So I think these two are the reasons that cause the situation where creator thinks it's easy while players don't.

Then optimal difficulty would be all difficulty in my perspective, as long as the level is making sense and work consistently.