Salt mine: one location through every upgrade level
Production buildings in a city builder are watched more often than anything else on the map, because the player returns to them every session. That is why the upgrade path is animated as one continuous shot rather than a set of separate states: the silhouette of the crater, the rock terraces and the shoreline stay locked, and the change happens in what fills the space around them - water in the ponds, fire under the boilers, cargo on the docks, people and carts on the walkways.
Everything moves in Spine on the client's own isometric assets, so the animation drops into the live build without new art or a separate render path. Each level is delivered as its own skeleton state, which lets the team show a single step during a real upgrade and reuse the same file for store and ad footage.