Shading 2d sprites - dark, not light.

Hello guys!

I am working on a doomlike FPS in Unreal and it is going well, but I noticed that all sprites are unlit. This is because they all share the default material of course, which is unlit by default. Now I managed to replace it with a lit material, but have not managed to get the effect that I want. My material is being lit alright, but when in shadow it retains the sprite’s normal color and appearnce, while it is coloured and light by any light source like crazy. I would prefer the opposite: the sprite would be its normal color when close to a strong light source, but goes black when in darkness. How get it to act in that way?

This is how my material looks now: