Lessons from Zymo - the necessity of a gameplay loop

28 Jul, 2026

TW: the game i'm reviewing is about body horror, which i’m not discussing in depth and leaving in the footnotes anyway if you wanna skip them, but be warned~! Also, naturally, spoilers for the mechanics of Zymo. I’ll leave info about the plot as sparse as I possibly can, as I’ll do anything in my power to not deter you from buying this book, god it’s so good.

So recently - not really recently, but i'm a slow blogger - i got my hands on what I can now confidently claim is my favorite RPG-adjacent book yet: Zymo, by Nalsco. Essentially, it's a choose-your-own adventure book, and it self-describes as “Openworld Viticultural Bodyhorror”. For the purposes of this review, what interests me most is the mechanics that make the game work as well as it does, so i'll mainly discuss the first part of that three-part statement, and try to answer the question:

Why Should a Choose-Your-Own Adventure Book Be “Open-World”?

The classic format of a choose-your-own adventure book is linear. Each event gives you two or more choices, which then branch off into more events, which then give more choices, so on until you reach an ending. This process is very tightly controlled by the author: each event has at most a few paths that can lead to it, and you’re certainly not expected to pass through the same event multiple times. On the other hand, Zymo does a really simple, but genius, thing: You have a map you view at the start of each phase of the day, some parts of which you can access freely, and some that require you to have accrued a certain amount of levels.¹ Once you gain said levels, and time goes on, the day re-starts, you can re-view the map, but this time with more parts of it available for discovery, so you thin go visit those parts that you previously couldn’t, and get more hooks to investigate when you’re even more levelled up.

The existence of this looping structure in Zymo is, in my opinion, why it feels like a true game, and why this is less true for choose-your-own adventure books. While a story is something you experience more or less passively, a game is something you actively play, something you’re supposed to become skilled at. And developing skill requires getting familiar with what you’re handling. And the most reliable way of becoming familiar with something is by getting repeatedly exposed to it, over and over again, which ordinary storybooks don’t do, by virtue of their linear structure. Instead, games (and here i’m talking about single-player games that are somewhat story-driven) - ever since there has been a “scientific” view of game design - have a gameplay loop, a series of actions you repeat over and over and over again, until you become skilled at performing those actions. The fact that you have to acquire skill in order to progress in the story is what gives games the possibility for a form of satisfaction that non-gamic media don’t have access to: the satisfaction you get for surpassing a challenge with your own skills. You’re not just admiring the ending someone else, the author, has cooked up for you, but you also feel personal accomplishment.

So what does this mean for the TTRPG-campaign-writing everyman?

There’s a reason why, in OSR-adjacent spaces, some campaign structures - like the West Marches, or a West-Marches structure applied to megadungeons - have so much staying power. Aside from being convenient as fuck for the GM, they’re also incredibly satisfying for the player: you take something that’s unfamiliar, and by getting exposed to it over and over, you become familiar with it, and that’s extremely satisfying from a game-design perspective, even if your game centers narrative. Zymo itself is very plot-centric work, and its gamic aspect only serves to enhance it.² We’ve been doing it since forever: the narrative behind Dark Souls (or any hard game known for its story) wouldn’t be a millionth as impactful if the game was easy.

So, put gameplay loops in your games! Make your players grow familiar with your worlds over time through repetition, challenge and just a tiny bit of frustration. And for god’s sake buy Zymo. Or at least look at its web page, as the art itself will surely do a better job of selling it to you than I ever could.

(Can you believe it? A fully illustrated book, made by someone who is prevalently an artist, being sold on how good its art is?)

#review