M-x control-air-traffic.

A week later - I helped out finishing the 4GL UI in the meantime and completed the messaging protocol - he called me in, quite happy. He showed me the code - page after page of Emacs Lisp, with exactly zero comments "because Lisp is self-documenting". I got scared, it was an air traffic control system after all, [...]

/u/cdegroot answering Do you use Emacs Lisp as a general purpose programming language?