I am in the process of writing a 2D game engine, and a dilemma emerged. Let me explain the situation...

I have a Scene class, to which various objects can be added (Drawable, ParticleEmitter, Light2D, etc), and as this is a 2D scene, things will obviously be drawn over each other.

My first thought was that I could have basic add and remove methods, but I soon realized that then there would be no way for the programmer to control the order in which things were drawn.

So I can up with two options, each with its pros and cons.

A) Would be to split the scene in layers. By that I mean instead of having the scene be a container of objects, have it be a container of layers, which are in turn the containers of objects.

B) Would require to have some kind of z-coordinate, and then have the scene sorted so objects with lower z get drawn first.

Option A is pretty solid, but the problem is with the lights. In what layer do I add it? Does it work cross-layer? On all bottom layers? And I still need the Z coordinate to calculate the shadow!

Option B would require me to change all my code from having Vector2D positions, to some kind of class that inherits from Vector2D and adds a z coordinate to it (I don't want it to be a Vector3D because I still need all the same methods the 2D kind has, just with .z clamped on).

Am I missing something? Is there an alternative to these methods?

I'm working in Javascript, if that makes a difference.