As you type, each character is colored along a rainbow gradient. The work
is done by rainbow-html from
rainbow.lisp, compiled ahead of time to a WebAssembly reactor with
--no-wasi (no imports, no GC host flags needed beyond
WebAssembly GC support). This page just feeds your text into the module's
rainbow-html(string) -> string export and drops the
returned HTML below. No server framework, no JavaScript color math.