The mist on the map
Land nobody has walked stays grey under a mist. Walk it, and it comes out in full colour and stays that way.
My first fog was a circle round the campfire. Inside it the world had colour, outside it everything was grey. It looked fine until I played it. On open ground the circle was really a diamond, because the reach is counted in steps along the ground, not in a straight line. Worse, when the scout walked out past the edge, the ground he had just seen stayed grey. The mist did not care who had been there.
What I actually wanted was simpler. The mist should be over land nobody has explored, and nothing else. So I threw the circle away. The game now keeps one bit for every tile: seen or not seen. Unseen land goes grey and pale, like a still morning mist. Seen land keeps its full colour wherever it lies, near the camp or far from it. The bits only ever turn on, so ground you have uncovered never goes back under.
People do the uncovering. Once a second, anyone outdoors who has moved clears the ground within 6 tiles of where they stand. Walk a path and the mist peels back along it, with a soft round edge instead of a hard square one.
The trees gave me the most trouble. They faded out with the distance, and a fading tree is drawn late, after the mist. So far away they stayed bright green inside the grey, like a few trees someone forgot to switch off. Now they fade by dither instead, and the mist covers them like everything else.
The film starts at 08:15 with the line between the two already on screen, grey plain on one side and green land on the other. The scout sets out, and by 09:57 the ground around him is in colour, with a soft edge where the mist begins.
I have not yet seen the mist on a mountain face, on a lake that is half in it, or at night. If something looks wrong there, I will find out when I play it.