I had this in mind for a while, but the idea of painting just the light from a window on a wooden floor appealed. So I painted it!
Quite simple to do, just painted the window parts fainter before putting the layer of yellow with gum arabic. Then some more layers on the boards and finally varnished.
The shinyness does not show very well in my bad photos so here is a view from the side:
You might be able to see the slight uneveness of the yellow light. Might have been better to be very careful with the added layers of yellow/gum arabic. I did let it dry well between coats, but maybe too much gum?
The final result is here