Learn Hardcore Swedish: Det blev mörkt tidigt, vilket gjorde promenaden kort. - It got dark early, which made the walk short.

Common patterns: Det är kallt. Det blev mörkt.
With a real subject, the adjective agrees with that noun:
- Kvällen blev mörk (kvällen = common gender)
- Rummet blev mörkt (rummet = neuter)

What’s the difference between blev and var here?

blev = became/got, emphasizes the change or onset: the moment when it started to be dark.
- Det blev mörkt vid fem.
var = was, describes a state at a given time.
- Klockan fem var det mörkt. Saying Det var mörkt tidigt is possible but less natural if you want to stress the onset; blev does that better.

Can I move tidigt elsewhere? For example: Det blev tidigt mörkt or Tidigt blev det mörkt?

Yes. All are grammatical, with slight differences in emphasis:

Det blev mörkt tidigt (neutral, very common)
Det blev tidigt mörkt (slight emphasis on how early)
Tidigt blev det mörkt (fronts the time adverb; still natural. Main clauses are V2 in Swedish, so the verb blev stays second.)

Why is there a comma before vilket?

Because vilket introduces a non-restrictive relative clause referring to the entire preceding clause. Swedish normally uses a comma to set off such comment clauses:

Det blev mörkt tidigt, vilket …

Why use vilket and not som?

When referring back to a whole idea/clause, Swedish prefers neuter vilket. Som typically attaches to a specific noun.

Good: Det blev mörkt tidigt, vilket gjorde promenaden kort.
More natural with som only if you insert a support noun: Det blev mörkt tidigt, något som gjorde promenaden kort.
Plain …, som gjorde … after the whole clause is usually avoided.

Does vilket agree in gender/number? What would it be for other antecedents?

Yes, as a relative pronoun it can agree:

Common gender singular: vilken
Neuter singular: vilket
Plural (any gender): vilka But when it refers to a whole clause or situation, Swedish uses neuter vilket by default. Note that with specific nouns, modern Swedish more often uses som instead of vilken/vilket/vilka unless the style is formal.

Why say gjorde promenaden kort instead of gjorde att promenaden blev kort?

Both are fine:

…, vilket gjorde promenaden kort. (concise, idiomatic “make NP adjective” pattern)
…, vilket gjorde att promenaden blev kort. (adds an explicit “that”-clause) You can also say …, vilket fick promenaden att bli kort, but that’s heavier and implies causation with an extra step.

Shouldn’t kort be the definite form (korta) since promenaden is definite?

No. After verbs like vara, bli, or in object complements after göra, adjectives are in predicative position and don’t take the definite -a just because the noun is definite.

Predicative: Promenaden var kort. / …gjorde promenaden kort.
Attributive (definite): Den korta promenaden. So here, kort is correct; korta would be wrong.

Would kortare work instead of kort?

Only if you want a comparative meaning: kortare = shorter (than expected/than usual/than something else). The original says the walk ended up short, not merely shorter than some baseline.

Are both mörkt and tidigt adverbs?

tidigt is an adverb (from the adjective tidig
- -t), modifying the time of the event.
mörkt here is the neuter predicative adjective (agreeing with impersonal det). It looks like an adverb because of the -t, but it’s functioning as an adjective. So they end in -t for different reasons.

Where would inte go if I want to negate something?

In the main clause, inte follows the finite verb: Det blev inte mörkt tidigt.
In the vilket-clause (a subordinate clause), inte comes before the finite verb:
- …, vilket inte gjorde promenaden kort.

Can I drop det and just say Blev mörkt tidigt?

No. Swedish requires the dummy subject det in weather/time expressions:

Correct: Det blev mörkt tidigt.
Incorrect: Blev mörkt tidigt.

Any quick pronunciation tips for key words?

det: often pronounced like “deh”; the final -t is typically silent in running speech.
blev: long e, like “bleev.”
mörkt: ö like the vowel in French “peur”; final -rkt is a tight cluster.
tidigt: stress on the first syllable, long i: “TEE-digt.”
vilket: initial v (never w); both vowels are short.
gjorde: gj is like English y; roughly “YUR-deh.”
promenaden: stress on “na”: pro-me-NA-den.

Could I use så instead of vilket to link the clauses?

Yes, but it changes the structure from a relative clause to a coordinating main clause:

Det blev mörkt tidigt, så promenaden blev kort. This is perfectly natural and a bit more conversational. Vilket sounds a touch more written/formal and comment-like.

Why the definite form promenaden? Could I say en promenad instead?

Promenaden implies a specific, contextually known walk (the one we took). Using en promenad would sound like “a walk” in general and is less natural here. You could also specify:

…gjorde vår promenad kort.
…gjorde kvällspromenaden kort.