I spent weeks reverse-engineering the original EXE and writing up a detailed spec of how the simulation actually works under the hood — population flow, elevator AI, the whole star-rating system. The specs are all on GitHub if you want to read them: https://github.com/phulin/tower-together/tree/main/specs
It's also collaborative. Multiple players can connect to the same tower, the simulation keeps running as long as anyone's connected, and build actions sync across clients in real time.
Because I rebuilt the UI, I could add features like shift-click to build grids of rooms - instead of painstakingly clicking to build rows of offices and hotels, shift-click allows a 10-floor grid to be built all at once.
The game runs on Cloudflare Durable Objects, one of my favorite web primitives.
Everything is open source: https://github.com/phulin/tower-together
There was a little-known sequel to SimTower called Yoot Tower (named after Yoot Saito). It was a commercial flop, but I played it in the 2000s and again in the 2010s and very much enjoyed it! It had a lot of added customizability (more choices of restaurants and shops, for one thing). I would love to see that game recreated.
I don't think I ever made it to the cathedral though.
EDIT: Nevermind... [sigh]
This is kind of the perfect use case though -- it's a game who cares if it's right or not.
...however I don't think that the source was ever published anywhere, considering that the repository still doesn't have the source code yet. ("Please check out the YootTower repo, where I'll publish the source code once it's cleaned up, reviewed and approved by Yoot, and relicensed with the MIT licensed.")