Square — esolangs.org/wiki/Square

JavaScript source
Square program
Square is an esolang where obfuscation is a block permutation puzzle. Programs are valid JavaScript encoded as a shuffled rectangular grid of 3x3 character blocks.
Encoder
1.
Escape: \s space, \n newline, \t tab, \\ backslash
2.
Pad escaped source with # to a multiple of 9
3.
Cut into N blocks of 9 chars and shuffle randomly
4.
Find the squarest rectangle: factor pair (W, H) of N with W ≤ H minimising |W−H|
5.
Output H row-groups of W blocks side by side, separated by blank lines
Interpreter
1.
Split on blank lines to get row-groups; split each group's 3 lines on spaces to recover N blocks
2.
Search all N! permutations with Heap's algorithm
3.
Unescape each candidate and attempt to compile as JavaScript
4.
First valid compilation wins — execute it
Execution semantics
The interpreter executes the first permutation whose unescaped content is syntactically valid JavaScript. This is not guaranteed to be the original program. Any permutation that happens to form valid JavaScript — however semantically unrelated — is a legitimate execution. For short programs this ambiguity is common; for long programs it is astronomically unlikely. The language is inherently probabilistic: encoding a program does not guarantee its recovery.
Complexity
N!
Search space grows superexponentially. Hello world = 6 perms (instant). Primes ungolfable = 10! = 3.6 million (~15 sec, unreliable). Primes golfed = 13! = 6.2 billion (~13 hours, measured). Primes minified = 20! (age of universe). Primes formatted = 36! (vastly longer).