"The boy was looking out of the window and thinking about something."

Translation: Мальчик смотрел в окно и о чём-то думал.

[Il-2]

Why is "Мальчик смотрел из окна и думал о чём-то" wrong?

[daal39]

I think that this is because смотреть в окно is a fixed expression that illustrates a way in which the Russian viewpoint is unique. What we think of as "looking out of a window" is to Russians "looking into a window." It makes sense for Duolingo to preserve this distinction.

[deactivated user]

It should be accepted too. I don't think there's any noticeable change in meaning.

[Il-2]

Thank you!

[Mactuary1]

В окно could be reserved for "looking at the window" (because there's something interesting about it).

[Roman_Key]

It would be translated as "Мальчик смотрел на окно"

[Pompey15]

"Мальчик смотрел в окно и думал о чём-то" - это правильный ответ, он должен приниматься или я не прав?

[Neon_Iceberg]

Yes, your choice is fine and should be accepted. Report it next time you will come across this task.

[AndroidKanada]

So чём-нибудь isn't accepted... is it wrong in this situation, or this this just an oversight?

[Scial]

If you are sure that the boy is thinking about something then it should be "чём-то". You would use "-нибудь" if it is just hypothetical.

[akyanzen]

Может он все таки "выглядывал' из окна?

[ChristinaSuko]

Мальчик выглядывал из окна и о чем-то думал. Reported it

[Roselet]

I'd translate your sentence as: The boy was peeking out of the window.

[Ajanni_Dawodu]

what case is чём-то in this sentence?

[Leslie509391]

Prepositional case. "About something" = "о чем-то".

[grekhovki]

"Этот мальчик..." is acceptable too

[tsooj]

That means this boy, instead of the boy.