Shading on 2D sprites?

So I’m screwing around with Unity 2D, and I am trying to make a level where everything is dark except where a light shines. I went into the render settings and changed the ambient lighting to black, but nothing seemed to change. Fog didn’t do anything either.

[19780-2d+shading+question.png|19780]

Then I realized, I didn’t know how to change the shading for a sprite in unity like you can a texture. And I think the problem is that the sprites are always self-lit, not responding to the environmental lighting. Is there a way to change that? Or do you have to write a custom shader? If so, I have no idea how to do that, so are there any shaders I could find online that I could stick on my sprites? Thanks for any help.

Create a new material and use the Sprites/Diffuse shader. Drag the material onto the ‘Material’ variable in the Sprite Renderer.