Sometimes, if you attempt to select a region and fill it in the sandbox, some pieces will be left out, and they are the spaces that were locked last time you were in game mode. Steps to reproduce:
Load sybypom (for example). Note how the pipes are shaded blue, but the yellow/black tiles are not.
Enter sandbox mode
Select a copier (for example) from the toolbox.
Select the whole thing using shift+click.
Press F
Notice that the squares that were shaded blue in game mode (the pipes) do not change.
Logged
if the_computer_is_turned_on and not the_computer_is_on_fire then do_stuff()
"He deflected my electric attack with a wall of water! That makes perfect sense!"