Trying to post something here every day or two, to keep up that momentum.
Done more work on multitile entites. I've been thinking, when a large entity moves, what happens to the things where it wants to move to?
Single-tile objects just swap positions. Large objects could do the same thing, but it seems more realistic to try to move stuff out of the way.
One recognized flaw with the current system for implementing falling multitile objects. It's possible for two "convex" objects to be molded around each other so that both hang in the air, each "supporting" the other. I'll probably handle this one by forbidding such objects. There are other solutions, we'll see if it becomes necessary to go that far.
The sandbox is being reimplemented now as a debugging aid.