Playback – Interactive Programming and Print Debugging Reimagined (in Clojure)

Tag'n'trace any Clojure(-Script) form to `tap` and Portal with automatic last-input function replay on eval, instant re-render and hassle-free insertion of traced data into the REPL.

Screencast's a bit rough, narration-less and musically questionable, but will hopefully still manage to give you a basic idea of what it's like to program like this.