Thank you for playing, glad you enjoyed it :D
For buildings to not overlap, just changing z-index wouldn’t fix problem, since entire building is one sprite. For example, if building exists at 2 different y coordinates and is not vertical, sprite in middle of those 2 would need to have z-index between those 2 y levels. Would have to split all building sprites into pieces at different y levels and make some changes in a way houses are generated for it to properly work.
That was planned, but, sadly, didn’t get time to implement.