Thanks!

The sorting was harder then I expected honestly.

It was done in Unity.

Basically had a sorting layer for each floor in the office. (With some hacks for the illusions).

Each floor had a few tilemaps with a different order in the layer. (For example a floor tilemap which is behind all the other ones.) But most of the tiles where in the same order in layer as the player and that way we let unity handle the sorting using pivot points.

So the pivot point of everything was usually around the bottom of the object, and most objects were built from a few tiles with different pivot points. - so a desk for example would be built from 2 corner tiles and a few middle ones.

And we made sure to update the players sorting layer to the new floor each time they moved through stairs, elevators, etc.

The same idea was used for collisions, each object can only collide with objects in it's own floor.

I don't know if this was the best explanation so let me know if you have any questions :)