What are the limitations on places that cannot be accessed by the Anywhere Door?

Okay, no problem! Talking about the Anywhere Door, I have so many thoughts! This was absolutely my most-wanted gadget as a kid, bar none. While it seems all-powerful, according to the various settings in the Doraemon manga and anime, it actually has quite a few "rules" and places it can't reach.

Let me break it down for you in plain language:

The Anywhere Door: Seemingly Omnipotent, But Actually Has Quite a Few "Rules"

Hey there! The Anywhere Door (Japanese: Dokodemo Doa) is definitely a star product among Doraemon's gadgets. Think of where you want to go, open the door, and you're there – a lazy person's dream, a travel marvel. But it's not a "bug-level" item that lets you do whatever you want; it has several crucial fundamental limitations.

1. Places "Not on the Map": The Unknown and Distant

This is the core limitation. How the Anywhere Door works is actually based on a built-in, ultra-high-precision map covering the entire universe.

Can't go beyond the map's range: While impressive, this map has a hard rule – it can only reach locations within 10 light-years of Earth. Think about it, 10 light-years is an astronomical distance (light takes 10 years to travel that far!), plenty for cruising around the Milky Way. But if you want to go to a farther galaxy, like Andromeda (2.54 million light-years away), the Anywhere Door is "out of service range."
Unknown coordinates won't work: If a place is brand new and never recorded (like a suddenly appearing mysterious island or a secret base just built by aliens), and the Anywhere Door's map system doesn't have its coordinates, you can't go there either. You'd need to reach it once by other means (like flying with the Take-copter) to let the map "record" the location before the door can be used.

(A simple diagram to help understand the concept of 10 light-years)

2. "Non-Normal Space": Barriers, Other Dimensions, and Stories

The Anywhere Door travels through the "three-dimensional physical space" we inhabit. If the target location is protected by special forces or simply doesn't exist within this spatial dimension, it's powerless.

Magic/Tech Barriers: In many feature-length stories, villains often use powerful technology or magic to create a "protective shield" or "barrier" around their hideouts. In these cases, the Anywhere Door won't open because it can't break through this spatial blockade.
Deep Sea/Earth's Core: While theoretically possible, many episodes mention that reaching extreme environments like the deep ocean or the Earth's core is very difficult, or even impossible directly. This is likely because immense water pressure or mantle energy interferes with the stability of spatial teleportation.
Storybooks/Paintings/Dreams: Want to use the Anywhere Door to rescue a princess in a fairy tale? Or enter someone's dream? That won't work. These places belong to "conceptual space" or "mental worlds," not the physical universe. To go to these places, Doraemon needs to pull out other specialized gadgets, like the "Fairy Tale Shoes" or the "Dream Machine."

3. "Time" Limitations: For Past and Future, Use the Time Machine

This is very important! The Anywhere Door can only move you through space at the "present" point in time.

It cannot take you to the age of dinosaurs, nor let you see your future self. Time travel is the exclusive function of the "Time Machine." You can think of it like this:

Anywhere Door: Handles space (Where to go?)
Time Machine: Handles time (When to go?)

So, trying to use the Anywhere Door to visit ancient times is absolutely impossible.

4. "Dynamic" and "Dangerous" Places: Safety First Principle

The Anywhere Door's design is quite "user-friendly"; it has basic safety logic.

Cannot lock onto fast-moving targets: Want to open a door directly into a car speeding down the highway or a spaceship traveling through the cosmos? This is very difficult. Because the coordinates are constantly changing, the door struggles to connect precisely.
Won't open in dangerous locations: You don't have to worry about opening the door to find a cliff, a volcano crater, or a solid wall behind it. The Anywhere Door has safety mechanisms; it intelligently avoids these lethal spots and automatically opens in the safest, most suitable position nearby. This is also why Nobita always lands safely when he uses it.

To Summarize

So, while the Anywhere Door is magical, its limitations can be simply summarized as:

Distance Limit: Cannot exceed 10 light-years.
Space Limit: Cannot go to places protected by barriers or not in the same dimension (e.g., stories, dreams).
Time Limit: Can only travel through space in the "present," cannot handle past or future.
Safety Limit: Cannot precisely connect to fast-moving targets and automatically avoids danger.

Looking at it this way, doesn't the gadget's setting seem more rigorous and interesting? Even 22nd-century black tech has its own "user manual"! Hope this explanation helps!