Learn Hardcore Japanese: kaze de mado ga yuremasu. - The window shakes because of the wind.

The particle で marks the cause or reason (here “because of the wind”). It can also mark an instrument (“with”), but in this context it tells us that 風 is the cause of the shaking.

Why is 窓 marked with が instead of を or は?

The verb 揺れる is intransitive (“to shake” by itself), so 窓 is the subject of that action and takes が. If you used を, you would need the transitive verb 揺らす (“to shake something”). は would mark it as the topic and could change the nuance, but here が is natural to introduce the changing state.

Could you use 風に instead of 風で?

Not in this simple sentence. 風に before an intransitive 揺れる is ungrammatical because に doesn’t mark a cause with intransitive verbs. You could say:
• 風のせいで窓が揺れます (“The window shakes because of the wind”),
• or use a passive with 風に: 窓が風に揺らされます (“The window is shaken by the wind”).

Why is the verb 揺れます in its intransitive form, and what does the ます ending indicate?

揺れる is the intransitive verb “to shake” (i.e. the window shakes on its own). Its ます form (揺れます) is simply the polite, non-past form—used in everyday conversation or writing to be courteous. Non-past can mean present or future.

Is the word order in 風で窓が揺れます fixed? Could I say 窓が風で揺れます?

Japanese word order is fairly flexible. You could say 窓が風で揺れます without changing the core meaning. The main requirement is that the verb (here 揺れます) comes at the end. Emphasis can shift slightly depending on what you put first.

Why are there spaces between words in 風　で　窓　が　揺れます? Are they required?

Spaces were added here to help learners identify individual words and particles. Standard written Japanese does not use spaces between words—the sentence would normally be written as 風で窓が揺れます。

Does Japanese have articles like “the” or “a”? How should I understand 風 here?

Japanese does not have definite or indefinite articles. Whether 風 means “the wind,” “a wind,” or just “wind” depends entirely on context. In this sentence it simply refers to “wind” in general.

If I want to emphasize that the wind actively shakes the window, how could I say that?

You can use the transitive verb 揺らす and mark 風 as the subject:
風が窓を揺らします。
This means “The wind shakes the window,” putting the wind in focus as the active agent.