Ahmed Amer's CSS-DOS project shows that a web browser can render and execute a Turing-complete IBM PC compatible emulator encoded entirely as a Cascading Style Sheet. The stylesheet is approximately 300 MB and contains a simulated Intel 8086 CPU, 640 kB of conventional RAM, a floppy-disk controller, and a VGA display controller. CSS now supports functions and conditional rules, but it is still an awkward foundation for ordinary sequential programs; Amer's key insight was that CSS's declarative, state-transition behavior maps more naturally onto hardware logic than onto software, making an emulator possible if not convenient.

The sheet is available at css-dos.ahmedamer.co.uk. It boots DOS, runs Windows 1.0, and starts id Software's DOOM. Performance is deliberately not the point: the emulated CPU executes about two machine instructions per second, not two frames per second. At that pace the article estimates a three-week DOS boot, a three-month level load, and DOOM rendered at roughly 0.0001 FPS. Amer has published a detailed write-up explaining the construction, including an interactive guide to the structure of the CSS file.