And if you make all board squares black, you would have the ultimate solid borders, which extend all the way to the square edge.
No, you would not. Any opaque or translucent background color is replaced with its fully transparent version after the SVG image is resized to a PNG. At present, this is done through a flood fill. For fully opaque black, the result is a loss of most of the border, as shown here:
I have already shown the result of a translucent black, and I have already mentioned that a fully transparent black gets the same result as a fully transparent white, which I previously illustrated. For the darkest borders, you can use an almost fully opaque black of #0000007e, as shown here:
No, you would not. Any opaque or translucent background color is replaced with its fully transparent version after the SVG image is resized to a PNG. At present, this is done through a flood fill. For fully opaque black, the result is a loss of most of the border, as shown here:
I have already shown the result of a translucent black, and I have already mentioned that a fully transparent black gets the same result as a fully transparent white, which I previously illustrated. For the darkest borders, you can use an almost fully opaque black of #0000007e, as shown here: