The Age of Light
Why all the rules for torches in caverns?
Rules for the darkness, for light and torches, spring up among OSR games like a new cockroach infestation - first you see one, but a thousand more hide in self-made dark recesses. And like cockroaches, the rules are not new. They're simply out in the light, presenting themselves. Because people used to know the darkness, and now they don't. So people make rules to show them how the darkness works.
Are you old enough to remember the darkness?
I once asked my grandfather about his experience with changing technology, and he told me about when light came to Scotland. He told me about the work and preparation, every day, to make sure the candles and lanterns could produce a flame, and the need to sit together, to use the light together. He knew the darkness well.
I knew the darkness from occasional power cuts. The candles, and sometimes the oil lantern would come out, and we would sit together in the light, playing board games. And sometimes I would take long walks, alone in the dark, because I was afraid of the dark, and I knew this was the only cure.
If you walk long enough in the dark in Scotland, you get a solid sense of how often stars come out (rarely), and the difference moonlight makes (all the difference). With good eyes, you can almost read a book by moonlight, and you can see people coming a long way off. Without it, you still see something - your eyes and brain conspire to make shapes, and you guess at the meaning of the shapes. The shapes always look a little like people, because we're made to spot people, and you just need to learn to not take that feeling too seriously. You're really just thinking 'road or not road?', and on the road you think 'puddle or not puddle?', and if you get those two questions right then you can walk for miles, by the light of the stars, filtered through the dense, Scottish clouds.
But you need more. Walking in the darkness makes you feel with your feet. The toes lift up a little more (even in shoes) and the feet throw out as you keep your weight back. And I bet a stick comes in handy, though I never needed one.
One the light goes out in the countryside, the house is a cave. You see nothing - half your eyes are just memory, and you keep your fingers on something to co-ordinate with your memories.
City-people generally know nothing of this, and humans are increasingly comprised of city-people. They come up to my village, and insist they can wear high-heels, and then turn on their phone's torch to see the road (blinding me completely). They grew up in the light. They slept in cribs, bathed in the neon street-light. They sleep by a phone so YouTube can glow into their eyes. Perhaps, when they get up to pee in the middle of the night, they turn down the volume and let YouTube shine the way.
I don't have any special RPG rules for the darkness, but I do have a platitude to share: you always see figures moving in the dark, whether or not they are there.