I don't know if Writeroom is still available (I downloaded mine YEARS ago) but it's a great text-writing program that turns your whole screen black and then it's just you and your typing.  In native green.  The first few months I had it, I kept instinctively typing in "would you like to play a game?" in before I did anything (I use Monaco as the font in that program but VT100 looks so much more "accurate").