Learn Hardcore Japanese: depaato de ha, kodomotati ga esukareetaa de asobanai you ni, tenin ga yoku mite iru. - At the department store, the staff watch carefully so that children don’t play on the escalator.

で marks the place where something happens: デパートで = at/in the department store.
は marks the topic (and often carries a slight contrast: “as for …”).

Putting them together:

デパートでは、…
≈ In department stores (at least / generally speaking), …

Nuance:

It sounds like a general statement about what happens in department stores.
There is often a weak contrast implied: “In department stores (maybe not in other places), clerks watch the kids.”

If you said only:

デパートで、子供たちが…
→ This would just mean “At a department store, children …” with less emphasis on “as for department stores (in general).”

So では marks “in department stores” as the topic/scope of the whole statement, not just a bare location.

There are two で’s: デパートで and エスカレーターで. Are they doing the same job?

Grammatically they are the same particle で, but they apply to different actions:

デパートでは
- で = place where the whole situation happens → in a department store.
エスカレーターで遊ばない
- で = place where the playing would happen → on the escalator / at the escalator.

So structurally:

デパートでは → the general setting: In department stores, …
エスカレーターで遊ぶ → the specific action: play on the escalator.

Both are “location of an action”, just for different verbs (the overall situation vs the specific verb 遊ぶ).

Why is it 子供たち and not just 子供? How does Japanese show plural here?

子供たち is the plural form: children.

子供 by itself is usually singular “child”, but in practice can also mean “child/children” in general, depending on context.
Adding たち makes the plurality explicit: 子供たち = children (a group of kids).

In this sentence:

子供たちがエスカレーターで遊ばないように
→ The focus is clearly on multiple kids possibly playing on the escalator, so 子供たち fits well.

You could say 子供が… and it would still be interpretable as “children” in this generic statement, but 子供たち emphasizes that it’s about kids as a group, which is natural for this safety context.

Why is it エスカレーターで遊ぶ? In English we say “play on the escalator”. Can で mean “on” here?

Yes. で here marks the place where the action of playing happens, which often corresponds to English “at / in / on”.

Typical patterns:

公園で遊ぶ – play at the park
家で遊ぶ – play at home
道で遊ぶ – play in the street
エスカレーターで遊ぶ – play on the escalator

English chooses prepositions (at / in / on) based on physical relationship; Japanese often uses で broadly for “place where an action takes place,” so “on the escalator” becomes エスカレーターで.

Note: エスカレーターで can also mean “by escalator” (go up by escalator), but with the verb 遊ぶ it’s clearly “play on the escalator”.

What exactly does 遊ばないように mean? How is this grammar built?

遊ばないように is:

遊ぶ (to play) → 遊ばない (negative form: don’t play)
遊ばない + ように

This pattern Vないように often means:

so that (someone) does not V / in order to prevent V

So:

子供たちがエスカレーターで遊ばないように
= so that children don’t play on the escalator / to prevent children from playing on the escalator.

Key point:
Here ように does not mean “like / as if”; it’s the purpose/result use of ように: so that ~ / in such a way that ~.

What’s the difference between Vないように and Vないために for “so that (something) doesn’t happen”? Why use ように here?

Both can sometimes translate as “so that ~ doesn’t V”, but they differ in nuance.

Vないように
- Focuses on aiming for a situation or controlling an outcome.
- Common in instructions, precautions, and soft commands.
- Sounds a bit softer / more natural when talking about preventing behavior.
Example:
- 怪我をしないように気をつけてください。
  Be careful so that you don’t get hurt.
Vないために
- Structurally is “for the purpose of not V-ing”.
- Often sounds a bit more deliberate or formal, more like a clear purpose/goal.
- Can feel heavy or awkward for everyday “please don’t do X” type behavior.

In this sentence:

子供たちがエスカレーターで遊ばないように、店員がよく見ている。
→ We’re talking about taking care / watching in order to prevent kids from doing something dangerous.
Vないように is the most natural choice for that nuance of “so that they don’t” / “to keep them from”.

How should I divide this sentence into clauses? Where does the “so that…” part end?

You can divide it like this:

デパートでは、
→ In department stores,
子供たちがエスカレーターで遊ばないように、
→ so that children don’t play on the escalator,
店員がよく見ている。
→ the clerks watch carefully / keep an eye on them.

So 子供たちがエスカレーターで遊ばないように is a subordinate clause of purpose that answers the question:

For what purpose do the clerks watch?
→ To make sure children don’t play on the escalator.

The comma after ように helps mark the boundary between:

the purpose clause (up to ように) and
the main action (from 店員がよく見ている).

Why is it 店員が and not 店員は? There’s already 子供たちが earlier; can we have two が’s?

Yes, you can have multiple が in one sentence when they belong to different clauses.

Structure:

子供たちがエスカレーターで遊ばないように、
→ Within this clause, 子供たちが is the subject: children don’t play…
店員がよく見ている。
→ In the main clause, 店員が is the subject: the clerks watch…

So each clause has its own が marking its own subject.

Why not 店員は?

店員が simply states who is doing the watching; it’s neutral, factual.
店員は would mark “the clerks” as a contrastive/topic, like:
- “As for the clerks, they keep a close watch” (implying perhaps someone else doesn’t, or some contrast).

Here, the sentence is a straightforward description, so 店員が is natural.

What does よく mean here? “Often” or “well”? How should I understand 店員がよく見ている?

よく has two common meanings:

often / frequently
well / carefully / properly

In 店員がよく見ている, both shades are relevant:

The basic idea is:
- The clerks are watching *carefully / closely (to prevent accidents).*
But in context, it can also suggest they are frequently / constantly watching.

So a natural translation is:

The clerks keep a close eye on them.
or
The clerks watch them carefully.

Either way, よく emphasizes attentive, thorough watching (and implicitly, quite a lot of it).

Why is 見ている used instead of just 見る? Does 見ている mean “are watching right now” or “are always watching”?

Vている has several uses; two relevant ones are:

Progressive: an action happening right now
- 今、テレビを見ている。 – I am watching TV (right now).
Habitual / repeated action: what someone generally does
- 毎朝ジョギングしている。 – I jog every morning.

In 店員がよく見ている, combined with デパートでは and no specific time expression, it is best understood as habitual:

In department stores, clerks *(habitually) keep watch so that kids don’t play on the escalator.*

So 見ている here does not just mean “are watching at this very moment”; it describes what clerks typically do (they are always keeping an eye on the kids).