Fantastic game, thank you for making this! I've spent many hours getting my character as big as possible and it was tons of fun.
That said, there is a funny bug at the very end. The character's weight can overflow, going from 2 billion wobbs to -2 billion wobbs. This immediately reverts them from the city to the apartment, which they are WAY too big for. Should be easily solved by checking the amount of weight to add isn't too high before adding it (i.e. if int.MaxValue - characterWeight < weightToGain, don't gain it).
But of course I always want to be bigger, so... I surmise from the values involved that weight is stored in an int32 (max value 2,147,483,647). First off you could easily double the cap by using an uint32 ("uint" in Unity C# code) instead. Being unsigned means it can't be negative, which seems fine because why would we want a negative weight. I don't think it would be a huge change to up it to uint64 ("ulong") or even UInt128 to support astronomical weights, which would be my dream.
This is probably a super nitpicky ask, and actually speaks to how engaging your game is that I spent enough time to get that far, but I hope you consider it. I'm really looking forward to what you decide to add in the future. Thanks for reading!