A good exercise and remark for the paper

We discovered today that Packard-Wolfram has a supposed solidification rule that is in fact Exactly 1 modified so that a 1 that is completely surrounded becomes a 0. This can be analyzed as another perturbation of Exactly 1. We have the tools to show that the final configuration is simply a checkerboard (and so has density 1/2) and that the state at any point in time is that checkerboard intersected with the corresponding state of the 1or2 rule. Work out the details and remember to include a remark in the write up.