Hi thank you so much for reading through!
The player has 2 Light2D nodes: one for ambiant (the big circle) and the flashlight. Both have a texture I made and I believe Light2D nodes automatically affect everything in the scene (there is an occlusion mask, pretty much like there is a physics collision mask, but I only used the first bit for everything, so everything in the scene is affected).
For shadows, Tilemap (the walls) have an automatic system to attribute an occlusion. I also added the possibility for objects to have a shadow (in which case the occluder goes on top of the object). I only used it on doors for the moment though. Maybe I could have an occluder on the floor for objects like tables or chairs which shouldn't fully block the player's view (unlike doors). However I think this shadow should be a little bit transparent (like the shadows I already drew for some objects (see the chair sprite)). I don't know if this is possible though, I'll have to check it out. Also a lot of people think that the bookshelves should cast a shadow, and I totally agree with that. But the system I currently have put the occluder directly on top of the object, so you wouldn't see the books if I did that.
So yeah I'll definitely work on this system in the future. Hope that helps!