How long did this game take, and how many people worked on it?
2 hours per day for all of the jam days. I am the sole developer, but I livestream this on twitch, so I have a rag tag group of malcontents and ne'er-do-wells that shout out bizarre ideas for the game. You'll be lucky in the end if there isn't a snail somewhere in the building.

What engine, language or tools did you use?
I use Visual Studio.

How did you implement the restriction and themes (if used)?
I took the limitation of "building" to mean an actual, literal building, and light to mean that lights levels were important, and decay to mean that decay was an important motivator in the actions the player must take.