Reverse Engineering SimTower

Tuesday, April 28, 2026 at 5:05 PM

I woke up the other day and asked: could an LLM reverse engineer a modern clone of my favorite childhood video game? So I did it. towers.world is live today and allows collaborative, coop play on a perfect clone of the original game.

The Clone

The Original

Thanks to this retrospective for the image.

At its core, the game is an elevator simulator. It starts getting hard when your tower grows and your sims contend with each other on getting where they want to go. For example, offices grow your tower the fastest, but they come with 6 sims on a synchronized 9-5 schedule that heavily loads your elevators. As a result, you have to manage very tightly what floors your elevators go to and when.

Unfortunately, the game is now basically impossible to play without an emulator. You could reimplement it if the engine were fully described somewhere—but it isn’t. My original idea was to have the LLMs reverse engineer the binary into a complete spec, and then use that spec to reimplement the game. I was inspired by Simon Willison’s posts on translating programs from one language to another—after all, assembly language is a programming language like any other, with well-defined semantics. Then I could add features like collaboration and better UI (primarily a build-a-grid-of-rooms feature).

So I did it. I started with the general binary reverse-engineering framework I’ve built, reaper. It’s a simple harness around a coding agent for static analysis: what can you learn about the binary from reading its disassembled code?

The Static Analysis Era

... continue reading