pairs.list

- (relationship)

ID_FLOAT <<-- ID_GLASS <--> ID_ARROW -->> ID_BELL

'float' & 'bell' is located high place. hard to reach.
so i want them to be passive. doesn't speak but only-listening.

'glass' & 'arrow' are a pair. and plus. they also speak to the high guys.

'glass' also speak to 'float'
'arrow' also speak to 'bell'