In Unity you need to create: New > Material, then choose Sprites/Difuse, set the color to pure black and add it to every single object to make it hide when no light is over it. Then, you need to add a source of light to your hero. Check this out: https://manygames.itch.io/thestrangebob
There is a hidden area to the left, destroy the boxes to get access. There, you will find a tower, inside this tower every object has this material.