I definitely identify with addressed concerns over the hassles of my go-to debug approach, viz. print statements. I have a rather intense state engine that, when things go awry, can be brutal to debug with prints. But now I am doing ClojureDart, which I know is on the FS roadmap. The state engine is stable these days, but if it misfires before you get to CLJD, forgive me if I swipe your idea and roll my own ad hoc, informally-specified, bug-ridden, slow implementation of half of FlowStorm. Maybe a tenth.