4.5 (ch. 27) Cellular Automata Orphans Are Not Culled

All tiles are considered "reachable" by the Dijkstra Map.

This results in orphan areas not being culled, and the possibility that completing a map might be impossible due to the exit stairs spawning in an orphan area.

Tested and verified with the "Run this chapter's example with web assembly, in your browser" link in section 4.5 of the tutorial