Questions & Answers about Skoðaðu þessa flík, er hún ekki retró?
Does the adjective retró change its ending to match the feminine noun flík?
No, it doesn't. Words ending in the slang or colloquial -ó suffix (like sveitó or krúttó) and international loanwords ending in -ó (like retró) are completely indeclinable. They stay exactly the same regardless of the gender, number, or case of the noun they describe.
Why does the sentence use hún (she) to say 'isn't it'?
In Icelandic, pronouns must match the grammatical gender of the noun they refer back to. Because flík (garment) is a feminine noun, you must use the feminine pronoun hún instead of the neuter það.
Why is the phrase þessa flík in the accusative case here?
It is the direct object of the verb skoða (to look at, to examine), which always governs the accusative case. This changes the nominative þessi flík to the accusative þessa flík.
What is the -ðu doing at the end of skoðaðu?
It is the pronoun þú (you) merged into the verb. When giving a command, Icelandic often attaches the pronoun directly to the imperative verb form, turning skoða þú into the single word skoðaðu.