On halfway of nine selected todo items I ran into a problem. There are some door type (lid) objects on top of stairs or sewers. Those objects are created on the same map as other objects that don't move, including stairs. When you create a hatch lid on stairs and open it the stairs are not displayed. More than that it also affects to object interactions (collision detection etc.).
The layer system of maps is already complex, but I could solve this by creating another layer for door type objects. Or I could create a stacked object map with std::list for each tile. Whatever the solution were it would also include collision detection logic etc. In other words a lot of work.
I was thinking of this for a while and decided to skip it. Just skip it for now. Lids are needed for sewers and in rare cases for stairs. It's not an important feature right now and because it's pretty big change to the engine I want to make sure that other more basic features are done first.