Z₂ Lattice Gauge Theory (Ising Model)
Edges represent Z₂ spins (thin = 0, thick = 1).
Each Monte Carlo step flips all four edges around a random plaquette,
accepted with probability 1/(1+exp(ΔE/T)).
The critical temperture is 2.27. Try quenching above and below this
temperature to see the different phases!