📄 Play Tetris in a PDF File

I'll let you decide if this one is fun or frightening! Whether or not this will work depends on your PDF reader or browser support, but it works with Chrome and Firefox, at least.

The PDF document format supports embedded JavaScript and this experiment uses it to implement a game of Tetris. The developer, Thomas Rinsma, has used Python to output the PostScript that includes the game's JavaScript. Couple that with the fact many browser PDF renderers are themselves implemented in JavaScript (e.g. PDF.js) and you have a veritable Matryoshka doll of technologies at play here.