The code that runs the world is the code no one reads.

誰も読まないコードが、世界を動かしている。

Start here — touch it.

In x = 5, is the 5 really inside x?

pythonVariables and referencesOpen dedicated page →

Source code

x =

❯ Try editing the highlighted part of the code above

Value to put in x5

Edit the 5 in the code above directly (or sweep with the slider). On the last screen, watch the boundary between 256 and 257.

Memory / executionStep 1 / 7

👁 What you can see ── first, the textbook picture: “put it in a box”

x = 5 is an “assignment.” Most tutorials describe it as “you put 5 into a box called x.” That picture is fine to start with. — But soon, when you ask Python whether two separately-made 5s are “the same thing,” the answer changes depending on the value. The secret is that 5 isn’t actually “inside” x. Let’s see why, step by step.

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Pick a question that intrigues you to open its piece.

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Today you wrote code again — or rather, you had it written.
We glance at the result, nod that “it works,” and move on.
Run it, it works, next.

But in the fraction of a microsecond that line runs —
values are copied, references tangle, memory is born and quietly discarded.
None of it shows. It doesn’t need to. So no one looks.

It works. Yet why it works, you couldn’t say.
That blank space spreads, quietly, beneath your feet too.

Backlucerna carries a single lantern down to where the light doesn’t reach.
What is really happening behind your code —
we made it walkable. One step at a time, at your own pace.

One step beneath “it works.”