Just in case you had started to believe that people were entirely out of new and creative ideas for running Doom, a GitHub user and high school student ading2210 has recently taken it upon themselves to port the classic first-person shooter to run inside a PDF file (as spotted by IGN!).
The port lacks the game's trademark sound and iconic colour palette of the original 1993 title, essentially being rendered in a 6-color monochrome output that basically amounts to frames of ASCII-art.
However, it is still unmistakably Doom, with ading2210 sharing an attention-grabbing video of a player running around the first level E1M1 blasting away hordes of zombies and demonic imps. It is currently playable inside Chromium-based browsers and was reportedly inspired by a similar project for Tetris, called PDFtris, which was created by the programmer ThomasRinsma.
According to its creator, the port is possible due to PDFs being able to support Javascript. As ading2210 states, they used Emscripten to compile Doom to an asm.js format, which they then used to run the game within the PDF engine.
The keyboard controls, meanwhile, are handled by typing commands into a text box or clicking buttons on screen to move the character around, toggle through menus, and fire weapons.
You can play the game here, if you want to check it out. Here's a link to the project's GitHub page, where you can find out more information.