[boothby]

Sadly, that depends on a discrepency between npiet and the current Piet spec:

> The interpreter now begins sliding from its current white codel, in the new direction of the DP, until it either enters a coloured block or encounters another restriction.

The npiet interpreter, instead, rewinds its position to the last colored codel upon peeking through whitespace. One of these days, I intend to add that behavior as an option to the lexer in my Piet compiler[1], but I haven't bothered yet.

Following the spec, the program is a trivial nonhalting loop because the extreme corners of almost all blocks are white-adjacent. Writing complex Piet programs to target multiple interpreters and compilers is quite the challenge, as they've all got subtly different undocumented interpretations of the spec. I think that the output of my Piet backend is more or less interpreter-agnostic, but I've only dug into the details of three or four other interpreters.

[1] https://github.com/boothby/repiet/