Ni meni se ne sviđa ta ideja.

Here ni means either / neither in a negative context.

So Ni meni... is like saying:

• me neither
• not to me either
• I don't ... either

It usually connects this sentence to something said before. For example, if someone already said they don’t like the idea, Ni meni se ne sviđa ta ideja means the speaker agrees with that negative statement.

Yes, but in Croatian this is normal and correct.

Croatian uses negative concord, which means multiple negative words can appear together in the same sentence:

• ni = neither / either (in negative contexts)
• ne = the negation on the verb

So Croatian keeps the verb negative even when another negative-type word is present.

A literal pattern is:

• Ni meni = neither to me
• se ne sviđa = is not pleasing

This is standard Croatian grammar, not a mistake.

Because the verb sviđati se does not work like English to like.

In Croatian, sviđati se means something like to be pleasing to.
That means:

• the person who likes/dislikes something goes in the dative
• the thing that is liked/disliked is the subject

So:

• meni = to me (dative)
• ta ideja = that idea (subject)

That is why Croatian says something structurally closer to:

• That idea is not pleasing to me either

rather than the English-style I don’t like that idea either.

Because meni is the full, stressed dative pronoun, while mi is a clitic (unstressed short form).

After ni, Croatian normally uses the full stressed form:

• ni meni
• ni tebi
• ni njemu

So Ni meni... is the natural form here.

By contrast, in a simple sentence without ni, you would often use the clitic:

• Ne sviđa mi se ta ideja.

That means the same basic thing, but without the either / neither idea.

In this sentence, se is part of the verb sviđati se.

It does not literally mean himself/herself/itself here in the way beginners sometimes expect from reflexive pronouns. Instead, you should learn sviđati se as a whole expression:

• sviđati se = to be pleasing / to appeal / to be liked

So:

• Sviđa mi se ta ideja. = I like that idea.
• Ne sviđa mi se ta ideja. = I don’t like that idea.

You generally cannot just remove se.

Because it agrees with ta ideja, which is singular.

In Croatian, the verb agrees with the grammatical subject:

• ta ideja = singular
• so the verb is sviđa = 3rd person singular

Compare:

• Ta ideja mi se sviđa. = I like that idea.
• Te ideje mi se sviđaju. = I like those ideas.

So the verb form depends on the thing being liked, not on the person who likes it.

Because ta ideja is the subject of the sentence.

With sviđati se, Croatian treats the thing liked as the subject:

• Ta ideja = that idea
• meni = to me

So ta ideja stays in the nominative.

This is different from English, where that idea is the object of like.
That difference is one of the most important things to notice with sviđati se.

Because ta ideja is nominative feminine singular.

The noun ideja is feminine, and here it is the subject, so the demonstrative must match it:

• ta ideja = that idea (nominative)
• tu ideju = that idea (accusative)

You would use tu ideju with a verb that takes a direct object, for example:

• Ne volim tu ideju. = I don’t like that idea.

But with sviđati se, the correct form is:

• Ne sviđa mi se ta ideja.

Yes. Croatian word order is flexible, and different orders change the emphasis.

For example:

• Ni meni se ne sviđa ta ideja.
• Ta ideja mi se ne sviđa.
• Ne sviđa mi se ta ideja.

All of these are natural, but they focus on different parts.

In your sentence, Ni meni is placed first for emphasis, as if the speaker is saying:

• I don’t like it either
• me neither

So the sentence is especially focused on the speaker’s agreement with a previous negative opinion.

Both can often be translated as I don’t like, but they are not exactly the same.

• ne sviđa mi se = it doesn’t appeal to me / I don’t like it
• ne volim = I don’t love / I don’t like, often more direct or broader

With ideas, plans, suggestions, designs, sviđati se is very common and often sounds especially natural:

• Ne sviđa mi se ta ideja.

If you use voljeti, the grammar changes because voljeti takes a direct object:

• Ne volim tu ideju.

So the meaning is similar, but the structure is different.

Yes. A useful literal breakdown is:

• Ni = neither / either
• meni = to me
• se ne sviđa = is not pleasing
• ta ideja = that idea

So a very literal English version would be:

• That idea is not pleasing to me either.

That literal structure helps explain:

• why meni is dative
• why ta ideja is nominative
• why the verb agrees with ideja