How do I make tile based darkness/light?

Hello,

I wonder how to make performance friendly tile based darkness and light.

I have 64x64 darkness tile, which is little transparent sprite and have them cover whole layout.

Then there are "lightsources" objects.

So, idea is that darkness should lose opacity as it gets closer to lightsource.

Haven't managed to get this work, and every tick solutions seems to impact performance...

Ideas?

Thanks.

I mean, its not that hard... I added line-of-sight for light source and if it sees darkness tile, I set its opacity

clamp(distance(Lightsource.X, Lightsource.Y, DarknessTile.X, DarknessTile.Y), 0, 100)

That works as long map doesn't have two lightsource, if I add one more, I think these start to conflict.

I think I should make so that darkness only react to closest light source but can't find how.