Homer Simpson in front of Moe's Tavern and King Toot's Music Store, with the Springfield skyline and the nuclear power plant behind him.
Work in progress OpenTSTO is an active, ongoing project rather than a finished piece of work. Systems are still being added and refined, and everything shown here is subject to change.

Preserving a beloved mobile game

The Simpsons: Tapped Out was a city-building mobile game that ran for over twelve years before its servers were shut down in January 2025. When a live game goes offline it stops being playable altogether – there is no offline mode to fall back on, and the client is useless without the service behind it.

OpenTSTO is a clean-room rebuild of that game's engine, written from scratch in C++20 so the game can be preserved and played again. It is built around exact preservation rather than reinvention: the rebuild runs on the original game's own scripts, assets and data files, and a change is only correct if it behaves the way the original did. The engine is cross-platform, running on Vulkan on PC and OpenGL ES on mobile.

The difficulty is that none of the original game's logic is documented. The compiled game carries no names or structure to work from, so every system — how quests unlock, how characters find their way around town, how a menu decides its layout — has to be recovered by studying the original, forming a theory about how it worked, and testing that theory against the real game before anything is built. Around 4,300 of the game's own data files have been mapped this way.

OpenTSTO is a joint effort. I lead the project and its design direction, working alongside BodNJenie, whose work on the server and backend systems the rebuild depends on.

My Role

  • Project lead, setting the direction and priorities for a rebuild spanning roughly 200,000 lines of code.
  • Specified how the quest and scripting systems needed to behave — objective tracking, unlock requirements, and the original's embedded scripting language — and verified each against the real game.
  • Designed the behaviour of the character systems, covering jobs, navigation around town, unlocks and costumes.
  • Rebuilt the game's interface against its original menu layout format, matching the source material closely enough to sit side by side with it.
  • Directed the reverse-engineering effort, validating findings against the running game rather than trusting assumptions — the difference between a system that looks right and one that behaves right.
  • Ran structured review passes across the project, catching behavioural mismatches that only surface in edge cases and documenting them so they stay fixed.

Original vs Rebuild

Drag the divider to compare the original game with OpenTSTO, and use the arrows to step between screens.

The store's Characters category, listing Lotto 'N' Liquor, Apu's Apartment, the Blue-Haired Lawyer and the Cracker Factory with their donut prices, rebuilt in OpenTSTO.
The store's Characters category, listing Lotto 'N' Liquor, Apu's Apartment, the Blue-Haired Lawyer and the Cracker Factory with their donut prices, in the original The Simpsons: Tapped Out client.
The Ho-ho-d'oh Pt. 1 prize track, showing the Elf Moe reward, locked decoration tiers, and a Collect Ornaments objective at 120 of 150, rebuilt in OpenTSTO.
The Ho-ho-d'oh Pt. 1 prize track, showing the Elf Moe reward, locked decoration tiers, and a Collect Ornaments objective at 120 of 150, in the original The Simpsons: Tapped Out client.
The Other Springfield friend map, with friend towns over a continuous shoreline and the Friendship Level 6 progress bar, rebuilt in OpenTSTO.
The Other Springfield friend map, with friend towns over a continuous shoreline and the Friendship Level 6 progress bar, in the original The Simpsons: Tapped Out client.
The Friend Level Prizes screen, showing Snowball II, Homer's Car and Stampy as unlockable prizes with E.A.R.L. up next, rebuilt in OpenTSTO.
The Friend Level Prizes screen, showing Snowball II, Homer's Car and Stampy as unlockable prizes with E.A.R.L. up next, in the original The Simpsons: Tapped Out client.

Work in progress — UI elements subject to be tweaked/changed, some features may appear incomplete or missing.

Development Log

A collection of images from the development of the game, showing the good and the buggy.

An early render test showing decoded .rgb image data in the custom renderer.
Town data decoded from the game's protobuf save format.
A first attempt at drawing BSV3 building graphics, with visible errors.
A later BSV3 building render, noticeably closer to the original artwork.
A depth sorting and positioning test, with buildings overlapping incorrectly.
An early terrain rendering test.
An early attempt at rendering roads across the town grid.
The game's splash screen running in Android Studio.
Boardwalk tiles rendering with an early depth-sorting pass applied.
A very early, incomplete render of the friend screen.
A broken MNT layout render of the account management screen.
The account registration screen.
An early implementation of the friend level prize screen.
An early implementation of the friendship level prize panel.
An early implementation of the level-up screen.