Preprocessor ↔ Dev tool to Transpile Code Superset to other (base compatible) Code

aka Preprocess

References

1. Sass ↔ Popular Superset extends CSS via Preprocessor

2. tailwindcss-cli ↔ npm CLI Dev tool to run PostCSS to Preprocess/Tree-Shake CSS

3. Directive ↔ Statement to direct Compiler/Preprocessor behavior