Evolution as understood by its ablest advocates is an inherently atheistic explanation. At least that is what Darwin thought. The misconception that evolution works towards a pre-determined goal is held by many high school and college students. According to neo-Darwinian theory, living things appear, and are the way they are, solely because of accidental changes in the genes conferring a survival advantage to the living things possessing them. Each random instruction represents a random mutation in an organism.
Every student has a different design because every student randomly picks different instructions.
The teacher then plays the role of blind nature, and chooses some shape to represent the feature favored by natural selection. Copies were then given back to all the students. After being collected by the teacher, it was again subjected to selection based on circular shape. Thus if pushed the analogy collapses, since evolution needs to explain above all the first origin of organisms, something left untouched by the simulation. Exercises of this sort can help students understand the real character of evolutionary theory.