Very cool!

At the top of the program you import Web Libraries. is it some standard Scheme web framework that you're using?

* ;; re-running this source bumps the generation; the old loop sees it ;; and lets go (js-eval "globalThis.__hero_gen = (globalThis.__hero_gen || 0) + 1") (define gen (js->number (js-get (js-global) "__hero_gen"))) (letrec ((tick (lambda _ (when (= gen (js->number (js-get (js-global) "__hero_gen"))) (frame!) (js-method (js-global) "requestAnimationFrame" tick))))) (js-method (js-global) "requestAnimationFrame" tick))

Is this the part where it is compiled?