Numberwang

For the brainfuck derivative, see Numberwang (brainfuck derivative).

NB: This language's specifications were changed on the 8th of August 2011.

Numberwang is a language created by Nathan van Doorn. It is inspired by Malbolge, Wang's basic machine B, and That Mitchell and Webb Look.

Programs in Numberwang are stored as a sequence of terminating decimals, delimited by "!". Whitespace is ignored.

Memory is stored on a bidirectionally unbounded tape, much like that esoteric programming language with derivatives that everyone loves to hate, brainfuck. Each cell has two possible values: marked, and unmarked.

At each step, the digital root of the sum of the current command, its position in the program, and the step number is calculated. The result modulo four is taken, and the appropriate instruction is ran:

The step number and command position all start at zero.

Computational Class
The computational class of Numberwang is unknown, but it is believed to be Turing-Complete.