I don’t know how much time Andy spent building the “poor man’s VM” system, but I know it was a significant effort that underpinned the rest of the game. The packer was something I probably put a few days into in the beginning (greedy and other trivial heuristics) and then kept improving in my “spare time” over the next year or so.

The packer was the final step after a level was pre-sorted and otherwise processed. It was quite fast, so it added only a little bit of extra time to the primary work of pre-rendering every frame of the level to recover the sort order (which typically took around an hour).

I did experiment with solver algorithms but they were so obviously going to be too slow that I abandoned the idea.