:: once upon a time, the primordial cloud of atoms condensated into a soup of small molecules, called A, L, FI, FO, FOE, Arrow, FRIN, FROUT and T.
Click and drag the atoms.
After click and drag the atom stays fixed.
Double click to release it.
Text near the atoms is not needed.
It is there only for your quick grasping of the notation.
Small atoms are called "ports".
radius of port = 3px for "left" text,
else radius = 1px for "right" or "middle"
color of port = yellow for "in" text,
else color = blue for "out" text