GraphvizFiddle

GraphvizFiddle draws DOT language [directed] graphs, see DOT User's Guide (on http://graphviz.org/).
It is an online code editor and playground for Graphviz dot layout tool, see blog posting for details.

DOT input & control   new/ʍǝu blog posting 2
initial scalable number rho-221 (from Graphviz Gallery: cluster crazy datastruct fsm hello switch)