Arrow colors

You can change the colors of the arrows and messages as followings:

a -[#red]> b : <color blue> some message</color>

Collections

There is a "collections" participant type:

collections "Things" as things

Hidden returns

There is sometimes some weirdness when returning after a self call when there is no explicit return. You can add a hidden return to fix this using:

a -> b++ : do stuff
b -> b : do stuff to self
b -[hidden]-> a : hidden return to fix weirdness