$'main'
 \-[100](!e!)-\  
              |
/----(!x!)0---/
|
|               /--s--1--(a)---m---------\
|               |                        |
|               \                        |
|                \              /-[1000]-/
\--(e)1s(!e!)--1i----(!a!)(a)0q<
 /                              \
/                               |
|                               |
\                               |
 >{~}q0(e)(!x!)a(x)-------------/
/
|
\-(x)o#

$ '~' (a -- b):
 \         
 |   /-t-\ #
 |  /     \|
 \-<       |
    \     /|
     \-f-/ @