Compra due gettoni, altrimenti non puoi giocare.

Yes. Here compra is the informal singular imperative of comprare (to buy), so it is a command addressed to one person that the speaker would call tu.

• Compra due gettoni. = Buy two tokens.

This form looks exactly like the lui/lei present tense form, but in this sentence the meaning is clearly imperative because it is giving an instruction.

Related forms:

• compra! = command to tu
• compri! = formal command to Lei
• comprate! = command to voi
• comprino! = formal/plural command to Loro (rare in everyday speech)

Italian often leaves out subject pronouns when they are already clear from the verb form or the context.

So instead of saying:

• Tu compra due gettoni (which would actually sound wrong here, because tu commands use just the verb)

Italian normally says:

• Compra due gettoni

The verb itself tells you that this is directed at you informally.

With commands, Italian very often uses just the verb:

• Vieni! = Come!
• Guarda! = Look!
• Ascolta! = Listen!

Gettoni is the plural of gettone. It usually means tokens, especially the kind used in machines, arcades, transport systems, or older public telephones.

Depending on context, English might translate it as:

• tokens
• coins
• chips

But the basic idea is a special token used to operate something, not just ordinary money.

Because gettone is a masculine noun ending in -e, and many nouns of this type form the plural in -i.

So:

• il gettone = the token
• i gettoni = the tokens

This is a very common pattern:

• il pane → i pani
• il fiore → i fiori

Not every noun behaves identically in all details, but -e → -i is a very common plural pattern.

Because after a number, Italian often uses the noun without an article when you are simply stating a quantity.

So:

• due gettoni = two tokens
• tre libri = three books
• quattro euro = four euros

If you say i due gettoni, it means the two tokens, referring to two specific tokens already known in the conversation.

Here the sentence just means buy two tokens, so no article is needed.

No. Due stays the same.

So you say:

• due gettoni (masculine plural)
• due monete (feminine plural)

Unlike uno/una, the number due does not change form based on gender.

Altrimenti means otherwise or or else.

In this sentence, it introduces the consequence if the command is not followed:

• Compra due gettoni, altrimenti non puoi giocare.
• Buy two tokens, otherwise you can’t play.

It is commonly used to connect two ideas:

1. do this
2. if not, this other thing happens

Examples:

• Sbrigati, altrimenti arriviamo tardi. = Hurry up, otherwise we’ll arrive late.
• Studia, altrimenti non passerai l’esame. = Study, otherwise you won’t pass the exam.

Yes. In many everyday situations, se no is a very natural alternative.

So you could also say:

• Compra due gettoni, se no non puoi giocare.

Both are correct, but there is a small difference in feel:

• altrimenti = slightly more formal or written
• se no = very common and conversational

In speech, many people would naturally use se no.

Because after the modal verb potere (can / to be able to), Italian uses the infinitive directly, without a preposition.

So:

• puoi giocare = you can play
• puoi entrare = you can enter
• puoi parlare = you can speak

This is the same pattern used with other modal verbs:

• devi studiare = you must study
• vuoi uscire = you want to go out
• so nuotare = I know how to swim

So a would be incorrect here.

Puoi is the second-person singular present tense of potere.

The verb potere means to be able to / can.

Present tense:

• io posso
• tu puoi
• lui/lei può
• noi possiamo
• voi potete
• loro possono

So non puoi giocare means you cannot play or you can’t play.

In Italian, negation with non normally goes before the conjugated verb.

So:

• puoi giocare = you can play
• non puoi giocare = you cannot play

More examples:

• capisco = I understand
• non capisco = I do not understand
• viene = he/she comes
• non viene = he/she does not come

This is one of the most basic and consistent negation patterns in Italian.

Giocare generally means to play, but the exact nuance depends on context.

In this sentence, because of due gettoni, it probably refers to playing a game that requires tokens, such as:

• an arcade machine
• a game table
• some kind of coin-operated game

So here giocare is not just abstract playing in general. It likely means play the game / use the machine to play.

Italian often leaves that object unstated when it is obvious from context.

The comma separates the sentence into two linked parts:

1. Compra due gettoni
2. altrimenti non puoi giocare

This is very natural in Italian because altrimenti introduces a consequence or warning.

The comma helps readability and mirrors the pause you would usually make in speech.

You will often see this pattern:

• Fai presto, altrimenti perdi il treno.
• Metti la giacca, altrimenti avrai freddo.

Yes, but not every change sounds equally natural.

The original:

• Compra due gettoni, altrimenti non puoi giocare.

Possible alternative:

• Altrimenti non puoi giocare: compra due gettoni.

That is grammatical, but it sounds less natural in ordinary conversation.

Also, putting altrimenti at the very end would usually not work the same way:

• Compra due gettoni, non puoi giocare altrimenti does not naturally mean the same thing.

That version sounds more like you can’t play otherwise / in any other way, which changes the meaning. So the original placement is the clearest and most idiomatic one.

It is informal singular because of compra.

So it is addressed to:

• one person
• in a tu relationship

If you wanted to be formal with one person, you would say:

• Compri due gettoni, altrimenti non può giocare.

However, in real life, especially in signs or spoken instructions, Italian may choose different wording to sound more natural, for example:

• Acquisti due gettoni, altrimenti non può giocare. (formal, but somewhat stiff)
• Bisogna comprare due gettoni per giocare. (more neutral, impersonal)

So the given sentence sounds like a direct instruction to someone you address as tu.