emptiness
^* is the bunt: the default value of a type, the same one =| pins.
^*
=|
^*(@) is 0.
^*(@)
0
irregular forms:
*type is ^*(type)
*type
^*(type)
$: makes a tuple mold, naming each face in a cell.
$:
$:(x=@ y=@) is the mold [x=@ y=@].
$:(x=@ y=@)
[x=@ y=@]