Attempt at simplification for https://ericlippert.com/2020/09/10/life-part-34/#comments

Gosper_with_4_steps.cs

        private static Quad UnmemoizedStep(Quad q)
        {
            Debug.Assert(q.Level >= 2);
            Quad r;
            if (q.IsEmpty)
                r = Empty(q.Level - 1);
            else if (q.Level == 2)
                r = StepBaseCase(q);
            else
            {
                Quad q9nw = q.NW.Center;
                Quad q9n = q.N.Center;
                Quad q9ne = q.NE.Center;
                Quad q9w = q.W.Center;
                Quad q9c = q.Center.Center;
                Quad q9e = q.E.Center;
                Quad q9sw = q.SW.Center;
                Quad q9s = q.S.Center;
                Quad q9se = q.SE.Center;
                Quad q4nw = Make(q9nw, q9n, q9c, q9w);
                Quad q4ne = Make(q9n, q9ne, q9e, q9c);
                Quad q4se = Make(q9c, q9e, q9se, q9s);
                Quad q4sw = Make(q9w, q9c, q9s, q9sw);
                Quad rnw = Step(q4nw);
                Quad rne = Step(q4ne);
                Quad rse = Step(q4se);
                Quad rsw = Step(q4sw);
                r = Make(rnw, rne, rse, rsw);
            }
            Debug.Assert(q.Level == r.Level + 1);
            return r;
        }