Running Doom in TypeScript’s Type System with Dimitri Mitropoulos - JSJ 684

What if I told you someone managed to run Doom inside TypeScript’s type system? Sounds insane, right? That’s exactly what our guest Dimitri Mitropoulos did—and in this episode, we dive deep into the how, the why, and the mind-bending implications of this ambitious project. From type-level programming to the philosophical limits of Turing completeness, this is an episode that pushes the boundaries of what you thought was possible in JavaScript.

We talk about how the TypeScript type system evolved to become Turing-complete, how Dimitri pulled off this seemingly impossible feat, and why “Doom-complete” might just be the new gold standard for computational capability. Along the way, we touch on functional programming, generics, recursion, and even some Lambda Calculus. It’s part computer science theory, part coding madness, and 100% geeky goodness.

Episode Highlights
[3:05] – Dimitri explains how a simple thought experiment turned into a year-and-a-half-long obsession
[8:40] – The origins and significance of Turing completeness in type systems
[14:15] – Why running Doom in TypeScript is more about proving limits than just showing off
[19:55] – What it means to run programs inside the type system vs. TypeScript code itself
[27:10] – ASCII art as output, functional recursion for game state, and hover-over frames in your editor
[35:30] – How ignorance, determination, and obsession fueled the completion of the project
[45:20] – Personal insights: balancing family, burnout, and passion while chasing an impossible dream

Links & Resources
Dimitri Mitropoulos
Michigan TypeScript YouTube Channel – Dimitri's channel featuring the project
Type Challenges by Anthony Fu – Advanced TypeScript exercises
SquiggleConf – The TypeScript-focused conference Dimitri co-founded
Josh Goldberg – TypeScript expert and co-organizer of SquiggleConf


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