An arch is simply a curve.

An arch is simply a curve., invented by User:A, is a self-modifying Arch-based language where the program itself is an arch. All commands are synonyms of different definitions of the word "Arch". It was partially influenced by Doug's variable structure, and partially influenced by the Arch data structure. It is designed to make programs be very hard to write; you have to eventually execute your data.

Specification

A cell in An arch is simply a curve. is 8 bytes, which is possibly specified in the Arch documentation (you can't represent 1.844674407371e+19 values with just one ASCII character anyway). Programs in An arch is simply a curve. will not halt.

An An arch is simply a curve. program will be run in an implicit infinite loop.

Instructions

The instruction counter is always 0, and the program right-shifts by default after a command (code executing backwards, that means you have to write code backwards)

Premier. (Push the value of the period register to the character after this command and shift the program right (avoiding executing that command).)
Primary. (Pop the character after this command and store this value to the register . (that is, the values of the register . represents a different ASCII character.))
Playful. (Move the code cyclically the value of the "." register times right.)
Semicircle. (Split the content of cell 0 into 2 cells with equal length.)

Short forms:

r.
y.
l.
e.

Self-extending Trivial cyclic execution system

y.r.