Light effects

I'm wondering how to create a light like the one in this video: http://youtu.be/rXDK6InUaO4?t=1m49s

I already know that lights doesn't apply on the sprites however I don't understand the light in the video. How is it possible that the background is still visible even if there is no light and after adding that light it just goes a bit red as the light flashes? I am new to Unity so maybe I just don't get something about the lights so please explain this to me. Let's say I just want to create regular level with similar light effects in some places, how should I achieve this?

Thank you very much.

 

There is a diffuse-lit version of the sprite shader. I think its located somewhere else in the shader hierarchy for some reason, but it's there. It's a surface shader which can accept light sources, from what I could tell.

 

I see, it's the Sprite/Diffuse shader. It makes the sprites a bit darker so I created directional light which somehow lights whole scene up so it allows to correct the color back. I also tried to make the flashing light effect, I created point light and it works as expected. Thank you very much.

 

Sure. Thanks for posting that video, i hadn't seen it.