Default value
null
Icons may appear differently depending on the icon state. For example, turf door icons could have “open” and “closed” states. If a state is specified that does not exist in the icon file, the default null state will be displayed if it exists.
turf/door
icon_state = "closed"
density = 1
verb
open()
set src in view(1)
icon_state = "open"
density = 0
close()
set src in view(1)
icon_state = "closed"
density = 1