Não avance; vai que o jogador muda a estratégia.

Avance is the negative imperative form used with você.

In Brazilian Portuguese, negative commands are normally built with não + present subjunctive:

• avançar
• que você avance
• não avance

So even though it looks like a subjunctive form, here it functions as a command: Don’t advance.

If you were addressing tu in fully standard grammar, it would be não avances. In Brazil, though, você-based command forms are extremely common.

Because Portuguese often leaves the subject unstated when it is clear from the verb form or the situation.

A command naturally implies the person being addressed, so não avance already means don’t you advance / don’t move forward without needing você.

You could say você não avance, but that would usually sound marked or unnatural in most everyday situations.

Vai que is a very common colloquial Brazilian expression used to introduce a possible situation, often one that justifies caution.

Depending on context, it can feel like:

• what if
• just in case
• maybe
• suppose that

So in this sentence, it gives the idea of don’t do that, because there’s a chance the player may change strategy.

Important: you usually should not translate vai que word for word. Literally, vai means goes, but in this expression it works as part of a fixed idiom.

Because after vai que, Brazilian Portuguese very often uses the present indicative, even though the meaning is hypothetical.

That is why forms like these are common:

• vai que chove
• vai que ele esquece
• vai que o jogador muda a estratégia

So muda is normal here.

If you want a more formal or more textbook-like structure, you would usually switch to a different expression, such as:

• caso o jogador mude a estratégia
• se o jogador mudar a estratégia

Those patterns use different grammar, but vai que + indicative is a very natural colloquial Brazilian pattern.

No. Vai que is informal and conversational.

It is very common in speech and in informal writing, especially when giving advice, warnings, or practical suggestions.

In more formal language, speakers would more likely use something like:

• caso
• se
• pode ser que
• talvez

So vai que o jogador muda a estratégia sounds natural and idiomatic in everyday Brazilian Portuguese, but not especially formal.

The semicolon links two closely connected parts:

1. the command: Não avance
2. the reason or caution behind it: vai que o jogador muda a estratégia

It creates a stronger pause than a comma, but it still keeps the two ideas tightly connected.

In informal writing, many people would also use:

• a comma: Não avance, vai que...
• a dash: Não avance — vai que...

So the semicolon is mainly a punctuation choice that gives a clear pause and structure.

Portuguese uses definite articles more often than English does.

Here, a estratégia refers to a strategy that is understood from the context: the player’s current or intended strategy.

So Portuguese naturally says:

• mudar a estratégia

where English might say either:

• change strategy
• change the strategy

Both ideas are possible in English, but Portuguese often prefers the article in this kind of sentence.

Both are possible, but they are not exactly the same.

• mudar a estratégia = change the strategy
  Focuses on the strategy itself as the object being changed.

• mudar de estratégia = switch strategies / change from one strategy to another
  Focuses more clearly on moving from one strategy to a different one.

In many contexts, the difference is small, and either one could work. In this sentence, muda a estratégia sounds very natural and simply means the player may change the strategy they are using.

Yes, but the tone would change.

For example:

• Não avance, se o jogador mudar a estratégia...
• Não avance caso o jogador mude a estratégia.

These are grammatically fine, but they sound more literal, structured, and less idiomatic than vai que.

Vai que adds a very natural spoken sense of caution, like:

• better not
• you never know
• what if that happens

So the original sentence sounds more like real everyday advice.

Very often, yes.

Speakers often use vai que when they want to be careful about a possible outcome, especially one that could create a problem.

Examples:

• Leva um casaco, vai que esfria.
• Salva o arquivo, vai que o computador trava.

So in your sentence, the idea is: don’t advance, because the player might unexpectedly change strategy, and that possibility is being treated as a reason for caution.