I literally JUST bought a Thumby out of a vending machine this past weekend, so this post feels a bit serendipitous for me. Thanks for sharing, and I'll have to check this out!
Small bug: the sim seems to double count residential population for taxes, industrial pop gets ignored. The duplicate logic seems to exist in UI but it's correct there.
Also I wonder if all the repetition could be reduced, or would it affect performance on MicroPython?
https://github.com/chrisdiana/TinyCity/blob/88d07cf98f13bb73...
Is it using the 1.3-inch monochrome OLED display of the Arduboy or something smaller? (Guessing the 72 × 40 display of the Thumby?)