An esolang

Only code divisible by p gets through.

Trapdoor is JavaScript with one extra rule: your program's source, read as one enormous integer, must be a multiple of a secret prime p. The lock below publishes N = p × q and nothing else. Everything you need is on this page.

N — practice lock (small, factor it yourself)

The workbench

Runs in a sandboxed worker, not the main page — a runaway loop here won't freeze the tab. N (a BigInt) is in scope. Use log(...) to print. Whatever you figure out here, you still have to type into the slot yourself.

idle

The slot

Whatever you paste here is what gets checked against p — byte for byte. If it's a multiple, the doors open and it runs, exactly as typed.

ACCEPTED

REJECTED

View source if you want to see how the lock is built — that's the point. One honest caveat: this page keeps p in ordinary browser memory, for illustration only. A real deployment would never ship p to a client at all; it would run the divisibility check behind a server that only ever answers yes or no. That version is written up separately if you want to see the difference between a demo and a design.