[Shadernoob Q#1] How to create a transparent 2d fog of war material!

Hello
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I am attempting to create a 2d fog of war effect. I am looking for the darkness to sit on top of my levels and then to have planes that can cut through the shadow to reveal the level underneath. I am also looking for the cut through effect to have a nice gradient and to not be a hard line
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I have these rooms:

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Now I will add in the shadow and I will show the desired effect that I am trying to achieve
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This MUST be a material that I can apply to sprties and planes because there will be many different elements that need to have this lighting effect
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What I have tried:
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I have made the shadow a customer vert/frag shader that had custom variables like player position and I rendered a hole that followed the player with the fuzziness around it to give it a nice gradient effect into the shadow. My issue with this is that I want to have many rooms that have this "lighting" effect and not just the player and I do not want to have to add custom variables to the shader every time I decide a new room needs to have this lightingthat would make any sane programmer vomit everywhere
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Using ColorMask 0 on a visibility shader that sat behind the shadow plane - this did work but I was not able to get the fuzziness / gradient effect around the edges as this just killed but it is the closet I have gotten.

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Any help at all would be much appreciated, just a wee hobbiest who is tired of smashing his head against my desk trying to get this to work ((((: