で
de
で is not a place marker. It is the ground you act on.
The picture Laying down a field before anything happens. Everything then moves inside that field. で is the field the action happens on; に is the point the action lands and stops.
Where the picture shows up in で
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the ground you act on
会議室で待っています。
kaigi-shitsu de matte imasu
I'm waiting in the meeting room.
A mat laid down in the meeting room, and you sitting inside it, waiting
Just being somewhere takes に; doing something there takes で. 会議室にいます is only being in the room.
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the thing that carries you
バスで通っています。
basu de kayotte imasu
I commute by bus.
Standing on the floor of a bus and being carried along on top of it
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what it is made out of
木で作りました。
ki de tsukurimashita
We made it out of wood.
The grain of the wood still showing on the surface of the finished thing
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the cause it came out of
風邪で休みました。
kaze de yasumimashita
I took the day off with a cold.
Lying under a blanket with a fever as the commute to work gets erased
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the span it fits inside
三十分で終わります。
sanjuppun de owarimasu
It'll be done in thirty minutes.
A job fitting exactly inside a box thirty minutes wide
All of it in one picture
で is the ground you lay down before anything happens. Lay down the meeting room and the waiting happens inside that room; lay down the bus and the travelling rides along on top of it; lay down wood and the object comes out of that material. Lay down a cold and the day off grows out of it; lay down thirty minutes and the work has to fit inside that box. Place, means, cause, limit — with で they are not five different things, they are all the same 'inside this'.