The author produce a playable PDF, a file that can be read both as a PDF document and executed as a Windows program: https://github.com/mwenge/iatheory/releases/tag/0.1

This is polyglot program

Iridis Alpha is a classic of the 8-bit home computer era. An innovative, side-scrolling shoot-em-up for the Commodore 64 published by Llamasoft in 1985 that was notable then and now for its technical accomplishment.

IRIDIS ALPHA THEORY unpacks the assembly code of the game and pores over it in minute detail. There are also lots of pretty pictures.

Discovered in Paged Out! issue #5