Learn Hardcore Japanese: kono eiga ha sugoku omosiroi kedo, betu ni nagaku ha nai. - This movie is very interesting, but it isn’t particularly long.

The first は in この映画は marks the topic, setting what we are talking about.
The は in 長くはない is contrastive, focusing the negation specifically on long. It implies not long at least, without claiming the opposite (short).

Why is it 長くはない and not 長くない? What is the nuance?

Both are correct negatives of 長い, but:

長くない: plain negation, not long.
長くはない: contrastive or partial negation, not long, at least. It avoids committing to short and sounds a bit more measured or contrastive.

Can I say 長いではない?

No. I‑adjectives negate with くない or くはない, not ではない. Use:

I‑adjective: 長くない / 長くはない
Na‑adjective or noun: 便利ではない / 学生ではない

What exactly does 別に mean here?

With a negative, 別に means not particularly or not especially. It is typically used with a negative ending like ない. Without a negative, 別に usually means separately or apart, as in 別に払う pay separately.

Is there a difference between 別に長くない and 別に長くはない?

Small nuance:

別に長くない: not particularly long, straightforward.
別に長くはない: adds a contrastive feel, not particularly long at least. In everyday speech, both are common; the は version can feel a touch more careful or contrastive.

Could I use 特に, そんなに, あまり, or たいして instead of 別に?

Yes, with nuance differences:

特に長くはない: not particularly long; neutral and safe in most registers.
そんなに長くない: not that long; implies comparison to some expectation.
あまり長くない: not very long; あまり prefers negative endings.
たいして長くない: not much long at all; can sound dismissive.

Why is it すごく面白い and not すごい面白い?

The adverbial form is すごく, which is standard before adjectives like 面白い. In casual speech, すごい面白い is very common, but すごく is more traditional and safe in writing or formal situations. You can also use とても面白い for neutral politeness.

Does 面白い mean funny or interesting?

Both are possible depending on context. 面白い often means interesting, engaging, or entertaining, not only funny. For specifically funny, you might say おかしい, 笑える, or ユーモラスな.

What is a fully polite version of the sentence?

この映画はとても面白いですが、特に長くはありません。
You can keep すごく if you like: この映画はすごく面白いですが、別に長くはありません。

Can けど end a sentence?

Yes. In speech, ending with けど softens the statement or invites a response, e.g., すごく面白いけど… implying but it has a downside or but what do you think. It is common and natural in conversation.

Why 映画は and not 映画が?

は marks the topic, which fits best for describing known information about the movie. が would mark it as the subject and often introduces new or contrastive focus, e.g., この映画がすごく面白い this movie (as opposed to others) is very interesting. Here, describing the movie’s attributes with は is the natural default.

Can I change the word order?

Within reason:

この映画は、すごく面白いけど、別に長くはない。 natural.
この映画、すごく面白いけど、別に長くはない。 dropping the first は is fine in speech.
すごく面白いけど、この映画は別に長くはない。 possible, but introducing the topic late can sound a bit marked.

Does 長くはない mean it is short?

Not necessarily. The contrastive は denies only long. It could be average length. To assert short, say 短い or あまり長くない if you mean not very long.

What is the role of the comma 、 after けど?

It marks a natural pause between the two clauses. In speech, you pause there; in writing, it improves readability. It is optional but recommended.

Is it okay to mix plain and polite forms with けど?

Yes, common patterns include:

面白いですけど、長くはありません。 polite throughout.
面白いけど、長くはない。 plain throughout. Avoid jarring switches mid-sentence unless for a deliberate effect; ですけど is a standard polite connector.

How is 別 read and what else can 別に mean?

別 is read べつ. As an adverb, 別に can mean separately or apart in non-negative contexts, e.g., 会計は別にします we will pay separately. With negatives, it commonly means not particularly.

Could I say そんなに長くはない instead of 別に長くはない?

Yes. そんなに長くはない means not that long, often tied to some expectation or comparison. 別に長くはない sounds more like not particularly long without a specific comparison point.

What does the く in 長く represent?

It is the adverbial or continuative form of an i‑adjective. I‑adjectives use く before ない for negation (長くない), before verbs like なる (長くなる), and in patterns like 長くはない where は focuses the following negation.