It worked lovely for a few months and now it doesn't do anything

WAYYY to black! Make it so you can change what color it makes it

Exactly what it says it is and works perfectly and easily.

This only changes the interface around the page, not the document itself, but if you go into File > Page Setup you can change the page background to black and then the text color to white. Works great for what I was looking for; probably the only thing I wish is that there was a lower contrast version, but with a pretty simple workaround, you get what you ask for.