World Options
Some settings are presentation: text speed, battle animations, window skin. A player who changes those changes what their own screen looks like, and nothing else. They stay on the client, where they belong.
Three settings are rules. They change what happens in a battle. In an online world those cannot live on the client, for the ordinary reason: a player who sets their own difficulty to Easy from their own machine is changing the rules the server plays by.
So MCE splits them. Presentation stays local. Rules come from the server.
Which is which
A census of the sixteen settings in the options screen sorts them into three groups:
| Group | Count | Where it lives |
|---|---|---|
| Rule | 3 | Server, seeded by the operator |
| Presentation | 12 | Client, the player's own choice |
| Hidden in online | 1 | Not shown at all |
The three rule settings are difficulty, trainer level and battle style. The hidden one is Auto‑save on teleporting, and it is hidden rather than shown read‑only because in online play the server owns persistence: an auto‑save toggle would be describing a thing that no longer happens.
How the client uses them
The client fetches the three values once, with mce_world_options_get, on its
way into the world.
The important design decision is what it does not do with them: it does not
write them into the player's own configuration. That was the first version, and
it was wrong. Those configurations are persisted, so a world set to Set would
have overwritten the player's Switch preference — and carried it into their
offline game, where no server rules anything.
So instead of writing, the engine asks. Each place that consumes a rule calls the reader for it and gets the world's value when there is a world, or the player's own when there is not. The player's preferences survive untouched.
Estilo: Fijo at the top of that screen is the world's value, not this player's —
they may well have Switch saved from their offline game, and it is still there,
untouched, waiting for them. Everything below the rules is ordinary local
preference: language, volume, animation speed. The server has no opinion about
those and never asks for one.
The options screen is wired to show the three as read‑only when the world rules them, so a player can see what difficulty they are on without being able to change it — the middle ground between hiding them (you cannot find out) and leaving them editable (you can cheat).
Measured on 2026‑08‑29 against a live server seeded to Hard/Set. The game's own
log, on the way into the world:
[R-OPCIONES] el mundo dice: dificultad=Hard estilo=Set aLaCaja=False sembrado=True
[R-OPCIONES] el mundo manda: dificultad=Hard estilo=Set aLaCaja=False
Two lines, and the second is the one that matters: the client fetched the rules and handed authority over to them. Both halves of the round trip say the same thing.
What the server does with them
Difficulty moves the level of trainer rivals — and only trainers, matching what Core does offline:
| Difficulty | Multiplier |
|---|---|
| Easy | 0.8 |
| Normal | 1.0 |
| Hard | 1.2 |
The result is clamped to 1–100. It is applied in buildTrainerParty, which is
the single place the server mints a trainer opponent, so there is no second path
that could disagree.
Seeding them
mce_world_options_seed is server‑to‑server only. It rejects any call that
carries a user session, and it needs the Nakama runtime http_key — the same
credential and the same rules as species seeding, which
means it must never be committed or shipped in a build.
The Hub's Online tab is the buyer‑facing path: you set the three values there and it seeds them for you, reading the key from outside the repository.
It rejects what it does not model, by name
Send a difficulty or a style the engine does not know, and the seed is refused, and the error says which value was wrong.
The tempting alternative was to accept it and fall back to Normal. That is
worse than it sounds. The operator would come away believing they had configured
a world, the world would silently be something else, and nothing would ever say
so. A rule the server cannot model is rejected, never resolved neutrally.
Not seeded is a distinct state
Storage starts empty, and empty means not seeded — which is deliberately not
the same as Normal, even though today both produce a multiplier of 1.0.
They are the same number now. What differs is what happens the day Normal
stops being 1.0: one of those worlds should change, and the other should not. A
server that collapsed the two would have thrown away the information needed to
tell them apart.
Permissions
The world_options record is stored with permissionRead: 2 and
permissionWrite: 0.
Everyone can read the rules they are playing under. Nobody can write them from a
client. There is no upload verb — mce_world_options_get only downloads, and
that absence is the design, not an omission.