SubWorld — from an old vision of an underwater world to an online RPG with an AI Game Master

A few years ago, I published the first outline of the SubWorld project. Originally, it was meant to be mainly an underwater strategy game — a future world where life on land had become only a distant memory, and people had to find their place in a reality dominated by oceans.

That idea is still somewhere in the plans. But over time, the project itself became much clearer, and I decided that the first step should be to try implementing something different.

Today, I see SubWorld not only as a strategy game, but as something much closer to my original RPG experience. Around eight years ago, I ran the first sessions of my own custom system on Steemit. These were classic tabletop-style sessions: players, characters, conversations, decisions, dice rolls, improvisation, and a Game Master who had to react to everything the party came up with.

For a long time, the right tools were missing to meaningfully bring this style of play online. I did not want to create a simple clicker game where the player only chooses one of several predefined options. In a real RPG, the most interesting things often happen when a player says: “Can I try doing it another way?”

Only now have the possibilities appeared to start implementing such a system in practice.

This is how SubWorld is being created — a browser-based RPG set in an underwater world, where classic session mechanics meet an AI Game Master.

From strategy to a living RPG session

The original direction of SubWorld placed more emphasis on the world, survival, and the development of an underwater reality. That foundation remains, but the way players enter this world has changed.

Instead of looking at everything only from a management perspective, the player takes on the role of a specific character. That character has their own stats, equipment, skills, action points, limitations, and possibilities.

This makes the world of SubWorld much more personal. It is not just about the fact that an underwater base exists somewhere. It is about your character actually stepping into a dark corridor, hearing the work of damaged generators, seeing traces of something on the floor, and having to decide what to do next.

Mechanics matter, but they do not lock players in

SubWorld has built-in mechanics: a map, locations, action points, tests, dice rolls, combat, equipment, damage, character progression, and an event journal.

A player can click an action assigned to a place, for example: investigate a clue, open a hatch, attack a threat, use a terminal, or search a body.

But that is only one layer of the game.

The second, much more important layer will be freeform narrative interactions described by players just like during a real RPG session.

A player will be able to write that they are trying to block a passage with an overturned cart, distract a creature with sound, use a flashlight to inspect a shaft, convince another character, prepare an ambush, improvise with tools, or solve a problem in a way that the system did not include as a ready-made button.

And that is exactly where the AI Game Master enters the game.

AI as the Game Master

The AI is not meant to replace the players. Its role is to act as a Game Master who organizes events, resolves the consequences of actions, and develops the world based on the party’s decisions.

At the end of a turn, the system gathers information: who did what, where each character is, what the dice results were, what the current state of the map is, which objects have been discovered, who is wounded, which threats have been defeated, and which ones still remain hidden.

Based on that, the AI prepares the response for the next turn. It can describe the outcome of a fight, reveal a new clue, open a passage, add a consequence of an earlier decision, or mark that something hidden has been alerted — even if the players do not know about it yet.

This makes it possible to combine predictable mechanics with the flexibility of a classic RPG session.

Characters, roles, and progression

Each character has their own profile. There are attributes, skills, HP, PSI, armor, action points, and equipment. Thanks to this, characters are not just avatars on a map — they have their own strengths and weaknesses.

Arven is a researcher and specialist in old systems and improvised repairs. He is better suited for terminals, data analysis, and technical workarounds.

Mara is an operator. She is good at fast action, reconnaissance, combat, and reacting to threats.

Torvin is the expedition’s security guard. He is tougher, more combat-oriented, and better prepared for situations where the party needs protection.

Characters gain experience and can develop their skills. This is important because, in the long run, each character should become increasingly specialized in a particular style of play.

Equipment matters

In SubWorld, equipment is not meant to be just a list of items. A weapon, suit, medkit, toolset, flashlight, or old diagnostic terminal can affect a character’s real possibilities.

A toolset can help open technical passages. A medkit can save a wounded character. A diagnostic terminal can allow someone to read old logs or understand the station’s systems. Weapons and ammunition matter in combat, but not every situation has to be solved with a shot.

A world that remembers decisions

One of the key assumptions is continuity of events.

If players open an airlock, the system should remember it. If they defeat an enemy, it should not suddenly appear again in the same place. If someone is wounded by toxic slime, that should have consequences. If the party makes too much noise, something hidden may react. If players ignore a clue, they may later enter a dangerous situation without full knowledge.

That is why the game records the state of the world, the journal, action results, discovered places, map changes, injuries, equipment, and the consequences of previous turns.

The first test scenario

The first scenario takes place in an abandoned underwater station. The party enters through an airlock, explores corridors, activates old terminals, fights threats, and gradually uncovers what happened there.

The map includes several sectors: the main corridor, entrance airlock, laboratory, communication hub, elevator shaft, service dock, and other areas.

Not everything is visible right away. Some threats remain hidden. Some passages must be discovered first. Certain pieces of information only appear after investigating clues or performing the right actions.

What already works?

At the current stage, the prototype already has several working elements:

test login, character selection, a map with locations and levels, actions assigned to specific places, dice rolls and test resolution, action points, HP, PSI, and armor, equipment, character journal, action result log, gameplay turns, AI Game Master response generation, local game state saving in SQL and JSON, the first scenario set in an abandoned underwater station.

It is still a prototype, but the direction of the project is becoming clearer and clearer.

What comes next?

The next stage is to improve freeform descriptive actions, interactions between players, combat, hidden threats, map secrets, equipment, and long-term consequences.

I want SubWorld to become something between a classic RPG session, an online game, and a narrative system supported by AI.

Originally, it was an idea for an underwater strategy game. Today, that vision has matured into a form much closer to me: a living RPG session set in a world beneath the surface.

This is only the beginning, but after years since the first sessions of my own RPG system, the tools finally exist to truly start bringing this idea to the internet.

If you would like to support the development of this game, I encourage you to follow this profile and support the posts with upvotes.