Ne csalj, miközben a barátod játszik!

Because Hungarian uses ne to negate commands and prohibitions.

• nem negates statements: Nem csalsz. = You are not cheating.
• ne negates commands: Ne csalj! = Don't cheat!

So in this sentence, ne is the correct choice because the speaker is telling someone not to do something.

Csalj is the 2nd person singular informal imperative of csal.

• csal = to cheat / deceive
• csalj! = cheat! / do cheat!
• ne csalj! = don't cheat!

This is the form you use when speaking to one person informally.

Yes. Ne csalj! and Ne csaljál! are both possible.

The shorter form, csalj, is very common and neutral.
The longer form, csaljál, can sound more colloquial, more emphatic, or just reflect personal/dialectal preference.

So both are grammatical, but Ne csalj! is a very standard choice.

Because Hungarian usually leaves subject pronouns out when the verb already shows who the subject is.

So:

• Ne csalj! already means Don't cheat!
• The hidden subject is te = you (singular, informal)

If you say Te ne csalj!, that adds emphasis, something like You be the one who doesn't cheat!

Miközben means while, while at the same time, or meanwhile.

It introduces an action happening simultaneously with another action:

• miközben a barátod játszik = while your friend is playing

A useful comparison:

• miközben strongly suggests two actions happening at the same time
• amíg can also mean while, but it can also mean until or as long as, depending on context

So here miközben is a very natural way to say while.

Because in Hungarian, a possessed noun can still take the definite article.

So:

• a barátod = your friend

To an English speaker, this may look like the your friend, but that is perfectly normal in Hungarian.

English normally does not combine the and your, but Hungarian often does. In this sentence, a barátod is the natural form.

The ending -od is the possessive ending meaning your.

• barát = friend
• barátod = your friend

Hungarian usually marks possession on the noun itself, instead of using a separate word like English your.

Compare:

• barátom = my friend
• barátod = your friend
• barátja = his/her friend

Yes, usually barát refers to a male friend, so barátod normally means your male friend.

If you wanted to say your female friend, you would usually say barátnőd.

However, there is an extra wrinkle: barát and barátnő can also mean boyfriend and girlfriend in the right context. In this sentence, because of the gaming context, barátod is most naturally understood as your friend rather than your boyfriend.

Hungarian does not have a separate progressive tense like English is playing.

So the simple present játszik can mean both:

• plays
• is playing

The context tells you which meaning is intended. After miközben, the ongoing meaning is the natural one, so English translates it as is playing.

If you want to make the ongoing sense even clearer, you can add éppen:

• miközben a barátod éppen játszik = while your friend is actually/in the middle of playing

Yes. Hungarian word order is flexible, and changing it often changes emphasis rather than basic meaning.

For example:

• Ne csalj, miközben a barátod játszik!
• Miközben a barátod játszik, ne csalj!

Both are correct. The second version puts the time/background information first, so it sounds a bit more like While your friend is playing, don't cheat.

Because miközben a barátod játszik is a subordinate clause.

Hungarian normally separates this kind of clause with a comma, just like English often does with while-clauses.

So the punctuation here is standard:

• Ne csalj, miközben a barátod játszik!

No. Csal is a broader verb.

Depending on context, it can mean:

• to cheat in a game or competition
• to deceive / trick
• to be unfaithful

In this sentence, because the other person is playing, the meaning is clearly to cheat in the game.

The command form changes depending on who you are addressing.

• Ne csalj! = don't cheat! (one person, informal)
• Ne csaljatok! = don't cheat! (more than one person, informal)
• Ne csaljon! = don't cheat! (one person, formal)
• Ne csaljanak! = don't cheat! (more than one person, formal)

If the possessive part also needs to match the addressee, that changes too:

• a barátod = your friend (singular informal)
• a barátotok = your friend (plural informal)
• a barátja = your friend (singular formal)