#+begin_src mermaid :file message-passing-01-intuition.png
%% mermaid graph showing basic message passing intution
%% for graph neural networks.
graph LR
%% subgraphs
    subgraph one[message]
    a1((A))-- fa:fa-envelope ---c1((C)):::orange80
    b1((B))-- fa:fa-envelope ---c1
    c1-- fa:fa-envelope ---d1((D))
    end
    subgraph two[aggregate]
    c2((C)):::orange80-. All messages .->c2'((C)):::orange50
    end
    subgraph three[update]
    a3((A))---c3'((C)):::orange50
    b3((B))---c3'
    c3'---d3((D))
    end
%% inter-subgraph
    one ==> two
    two ==> three
%% styling
   classDef orange80 fill:#ffcc99
   classDef orange50 fill:#ff8000

%% references
%% https://mermaid.js.org/syntax/flowchart.html
%% https://www.w3schools.com/colors/colors_picker.asp
#+end_src

#+RESULTS:
[[file:message-passing-01-intuition.png]]