HUNTER, invented by Chris Pressey in 2001, is a deterministic particle automaton based on mazespace-rewriting and critter-style message passing (and also an esoteric programming language). The language attempts to solve the problem of programmer boredom leading to the abandonment of software.
HUNTER was submitted to the 2001 Esoteric Awards.
A program is composed of mice in a space interacting with cheese and each other. The detailed description is copyrighted, but can be found here.