This seems to match how CC2 actually works, and it fixes the replays for
the CC1 levels BLOCK BUSTER, THE PRISONER, CATACOMBS, and GOLDKEY.
Unfortunately, it also regresses ON THE ROCKS, GRAIL, and ALPHABET SOUP,
and I do not know why. I'm not even sure why it fixes CATACOMBS and
GOLDKEY. It makes a mess of force floor handling with mixed results.
It's also some 40% slower, which is not ideal.
I doubt I'll revisit this particular branch, since it's the sort of mass
code rearrangement that breaks everything, but I'm keeping it for future
reference in case I try to revisit this idea.
86764612d3