Learn Croatian: Svaka epizoda je puna preokreta, zar ne? - Every episode is full of twists, isn't it?

Here, zar ne acts like a tag question in English, such as "isn't it?" or "right?". You add it to the end of a statement when you expect the listener to agree with you.

Why is the word for "twists" in the genitive case (preokreta)?

In Croatian, the adjective pun (full) requires the noun that follows it to be in the genitive case. This is very similar to how we need the preposition "of" in the English phrase "full of".

Is preokreta singular or plural here, since both genitive forms look the same?

It is genitive plural. The base noun is the masculine word preokret (twist). Its genitive singular and genitive plural are both written as preokreta, so you have to rely on context. Here, a TV episode is full of multiple twists, so it translates as plural.

Why do we use the feminine form puna instead of just pun?

Puna describes the subject of the sentence, epizoda (episode). Since epizoda is a feminine noun, the adjective must take the feminine singular ending to match it.