Learn Hardcore Russian: Перед сном не стоит увеличивать яркость экрана. - Before sleep, it’s not worth increasing the screen brightness.

Here не стоит + infinitive is an impersonal “advice” construction meaning it’s not worth doing / it’s better not to / you shouldn’t.
It’s unrelated to prices in this sentence, even though стоить can also mean to cost in other contexts.

Why is it стоит (3rd person singular) if there’s no subject?

This is an impersonal sentence: Russian often gives recommendations without an explicit subject.
You can add a “logical subject” if you want:

Перед сном вам не стоит увеличивать яркость экрана. (Before bed, you shouldn’t increase the screen brightness.)

But the version without вам is very common and natural.

Why is it увеличивать and not увеличить?

Увеличивать is imperfective, used for general advice / a repeated or typical situation (“as a rule, don’t do this before bed”).
Увеличить (perfective) would sound more like a single one-time action in a specific situation:

Перед сном не стоит увеличить яркость экрана = “It’s not worth increasing it (this time).” (less neutral as general guidance)

Why is it перед сном and what case is сном?

The preposition перед requires the instrumental case.
сон (sleep) → instrumental singular сном.
So перед сном literally means “before sleep / before going to sleep.”

Is перед сном the same as до сна?

They’re close, but перед сном is the most natural everyday way to mean right before going to bed / before falling asleep.
До сна can sound more abstract or less idiomatic in this exact “bedtime routine” sense.

What’s the grammar of яркость экрана? Why is экрана in the genitive?

Яркость is the direct object of увеличивать, so it’s in the accusative (same form as nominative for this noun).
Экрана is genitive because it means “brightness of the screen” (a “noun + noun” relationship like possession/association).

Could I add своего (my/your/one’s) here: яркость своего экрана?

Yes, but it’s usually unnecessary because the context already implies “your screen.”

Neutral, general advice: …яркость экрана.
More explicit/personal: …яркость своего экрана.

Why is the sentence ordered like this? Can I move перед сном?

Putting Перед сном first sets the time frame (topic) right away, which is very common.
Other word orders are possible:

Не стоит перед сном увеличивать яркость экрана. (also natural)
Не стоит увеличивать яркость экрана перед сном. (fine, slightly more “afterthought” timing)

How does не стоит differ from не надо, не нужно, or нельзя?

не стоит = “it’s not worth it / better not to” (soft, advisory, polite)
не надо / не нужно = “don’t / you don’t need to” (more direct, practical)
нельзя = “it’s forbidden / not allowed” (strong, rule-based)

So не стоит sounds like friendly health/comfort advice.

Is this sentence formal or informal?

It’s neutral and fits both everyday speech and written recommendations (health tips, phone settings advice, etc.). It’s not slangy and not overly formal.

Any key pronunciation/stress points I should know?

Common stress points:

перед (pe-RED)
сном (single syllable)
стои́т (sto-EET)
увеличива́ть (u-ve-lee-chee-VAT’)
я́ркость (YAR-kust’)
экра́на (e-KRA-na)