Bloodnok,
Actually, I started with the premise that it was a weighted undirected graph and tried to find a heuristic algorithm for the longest path problem. Unfortunately, this doesn't work because the graph itself changes every time you make a decision. In other words, what is connected to what (starting at level 2) changes each step you take. Perhaps this works to my advantage (no longer NP complete) but I haven't figured it out - which is why I asked for suggestions.