Making light matter and keeping track of those light sources in your oldschool(ish) dungeon adventure can be a chore especially since it is so mathy with no real way to directly relatable gameness betond "mother may I" for if things can be seen or not. I may have read parts of this elsewhere in other game materials, if you have too let me know I want to share the credit and improve the idea if I can.
This idea literally just struck me moments ago after replying to my last post. There's been no play-testing of this in my campaign just yet but by gum I think it might just work.
Each party has a Brightness score. This score measures how much light the part has on hand. "Ooooh amazing" you say another score to track! Yes but... what this score impacts is what is important. Most simply the Brightness governs the impact the party can have in a dark environment. Brightness determines how effective the PCs and NPCs that need artificial light sources can be (it also has other uses I'll get to).
Obviously enough how bright it is impacts what you can see in an otherwise dark environment. So when was the last time it mattered in a game if you were trying to do something by the light of a candle, a matchstick, or a glowbug lamp? It matters all the time in real life so why not in our RPG adventures.
So this Brightness score acts sort of like the "passive perception check" in new-fangled talk, if it's bright enough you can see it... pretty simple isn't it? But we don't just stop there this Brightness also serves as a soft cap to how well the PCs can do anything within the illumination. So let's say Brightness is 18 well guess what any d20 roll a player is making to impact the environment or NPCs is "capped" at that score of 18 if sight is generally a requirement to get the act done. I say a soft cap so that way when players roll really well we don't totally ruin everyone's fun. This cap shouldn't impact critical hits or similar special success. Any easy way to keep this penalty "soft" is to apply a negative adjustment to any (non-critical) roll over the Brightness score. I'm thinking a modifier of -4 or -5 would generally do the trick with d20 rolls as it is inline with the classical darkness/invisibility penalties and when a party is say down to 0 Brightness it would have the identical effect on play
With Brightness having such a large impact on play it's going to be something that is going to get a lot of attention by the players. But let's not stop there. The Brightness can also serve as the morale score light adverse dwellers of the dark have to check against when they normally would be making morale checks. The lights the party are carrying into the depths of the underworld all of a sudden matter a lot more. The more something maters the more the players will be willing to track it.
We can go one step further and have this brightness score inflict a penalty on such creatures particularly tied to shadow and darkness and one easy way to do this is have the brightness score determine the minimal hit roll required by monsters to hit PCs and their minions within the brightness... the Brightness becomes the worst ac score (if yuo are counting up for AC) anyone can have against creatures bound to darkness. This is major change but not an illogical one, I'm not recommending it impact all underworld monsters but shadows, some demons, and some undead could surely be impacted in this manner.
Of course with this Brightness being so important in play it also serves as a score the baddies and misfortune can attack in the course of an adventure. The Brightness score itself serves as the lights own AC and HP score against all those attacking it. Time itself may just knock down that score 1 point a turn or by a couple points each time "lights flicker" comes up on a random encounter check.
With Brightness producing limits and strengths for he party there is more reason for players to track it and much more reason for players to remember to have their character bring torches and lanterns.
Still have to figure out campaign appropriate levels of brightness for different sources. It shouldn't be difficult at all to get up to 12 -15 or so but going higher should be tricky (maybe requiring "checks" against the parties own Brightness score...??). It would be very simply to do 1d6 for a candle, 1d8 for a torch, 1d10 for a lamp and add them up. Don't worry how far PCs are from each let the Brightness score be a shared pool for the whole party as long as they don't actually separate over very large spaces(I don't want to track where all the characters are every moment of the game in inches and such).
Hmmm.... final note... how "far" can a party see? No problem at all within a number of feet (even yards/meters if you are a softie) from anyone holding a light source equal to the Brightness. Beyond that things get shadowy...