Se calhar um seis, subtrai dez e vira o baralho.

No. In this sentence, se calhar does not mean maybe.

Here it is:

• se = if
• calhar = a verb meaning to happen by chance, to come up, or to be drawn

So Se calhar um seis means something like If a six comes up.

This is easy to confuse with the very common European Portuguese expression se calhar = maybe/perhaps:

• Se calhar, chove amanhã. = Maybe it will rain tomorrow.

In your sentence, the rest of the structure shows that it is the verb calhar, not the fixed expression se calhar = maybe.

In this kind of context, calhar means to come up by chance, to turn up, or to be the one that appears/is drawn.

So with a number, card, or result, it can mean:

• a number comes up
• a certain card is drawn
• a certain result happens by chance

Here, calhar um seis is basically for a six to come up.

In game language, English might use:

• if a six comes up
• if you draw a six
• if a six turns up

The exact English wording depends on the game.

Because Portuguese often uses the future subjunctive after se when talking about a future possibility or condition.

So:

• Se calhar um seis... = If a six comes up...

The tricky part is that for many verbs, the 3rd person singular future subjunctive looks like the infinitive. That is what is happening here.

Compare:

• infinitive: calhar
• future subjunctive, 3rd person singular: calhar

So this is not the plain infinitive in meaning, even though it looks the same. It is the normal form after se in this kind of sentence.

Because Portuguese often places the verb before the subject in clauses like this, especially when talking about something happening or turning up.

So:

• Se calhar um seis... sounds natural
• um seis is the subject

It works a bit like English:

• If a six comes up...

English also puts the verb before the idea of the result in that phrasing. Portuguese is doing something similar here.

Because um seis means a six: one result/card/value of six.

That is very natural when talking about:

• a die result
• a card
• a numbered token
• any single item with the value six

So:

• um seis = a six

Without um, seis would more naturally mean just the number six in a general sense, not a single six showing up.

Yes. Here they are being used as imperatives: direct instructions.

So:

• subtrai = subtract
• vira = turn over / flip

The implied subject is tu:

• (tu) subtrai
• (tu) vira

This is very common in game rules, instructions, and step-by-step directions.

Because Portuguese often leaves the subject pronoun out when it is clear from the verb form or the context.

So instead of saying:

• Tu subtrai dez e vira o baralho

Portuguese normally just says:

• Subtrai dez e vira o baralho

That sounds natural and concise in instructions. English usually needs you, but Portuguese often does not.

Baralho means deck of cards.

So vira o baralho means turn over the deck or flip the deck.

It does not mean shuffle the deck. For shuffle, Portuguese would use a verb like:

• baralhar
• sometimes embaralhar

So:

• vira o baralho = flip/turn the deck
• baralha o baralho = shuffle the deck

Most likely, yes.

The basic meaning of virar is to turn, to flip, or to turn over. In a card-game context, virar o baralho usually means to physically change the deck’s orientation, often to reveal or reposition it according to the rules.

The exact action can depend on the specific game, but it is about turning/flipping, not mixing the cards.

The comma separates the condition from the main instruction.

So the sentence is structured like this:

• Se calhar um seis = the condition
• subtrai dez e vira o baralho = what you do if that condition is met

In English, we often do the same:

• If a six comes up, subtract ten and flip the deck.

So the comma is helping to mark the conditional clause clearly.