I started a short story... it took me 3.5 years and ended up being over 600k words...I second this. I've added H5 to scripts I study to learn how to write episodically. I do fine with short story, am working on a novel, have done a couple novellas, but struggle with turning a plot into episode-sized chunks from the beginning. (I usually end up writing chapters, then rearranging them after the fact, often pulling scenes out of one chapter to drop into another or swapping chapters whole.)
Did I mention I am not good at short and to the point?
But unless you are doing a kinetic novel, game writing is another beast entirely, factoring in player choice can be daunting for some, and the more options you give, the more branches you might need (depending on how much influence the player is to have on the world).
This is why I started a timeline. It's good to plan as much as you can out ahead of time.