At the moment, I'm working on some design for my spare time project I've been talking about earlier; Iskall.
The challenge I'm currently working on is to have the story, its events and the introduction of new gameplay elements to work together.
The game's overall story is set. There are a few scenarios in it, not dependent on being in a particular order to work. And all the themes for the levels are set. Right now, they're all listed in the order that makes most sense and creates the best narrative, experience and allows for some nice transitions between the levels. That is, if you only look at the story.
But here's the catch. Many of the events are directly intertwined with the introduction of new gameplay mechanics. For me, gameplay always comes first, but sometimes you have to compromise since a game is not only mechanics, it's an experience to be had by the player.
Let's draw a parallel to Super Mario Bros.. Nintendo could have introduced the Mushroom that turns Mario into Super Mario during the last levels, but it was better for the game to introduce it in the very first level. I can introduce some of Iskall's stuff very late, but it'll be better if it's early and vice versa.
And also, some events are directly tied to a specific level. Some events I can move freely between the levels, while some must be at specific theme.
Meaning, different story sections have different dependencies like theme, level and gameplay mechanic.
I have a chart showing in what order and when I want each new gameplay element to be introduced. Stuff like new enemies, new abilities, etc. But just cutting and pasting in the story to accomodate that chart doesn't result in a tight presentation context-wise. So what I'm doing right now is to find that balance.
I don't have a sure solution for this, and I don't know how it'll end since I'm not done yet. But the way I'm approaching it is to try and constantly look at the big picture and I'm trying to spread it out, so all the good stuff isn't too close together.
There will have to be some editing from both ends to make it feel just right.