Double Feature: Movement & Light
In this article, I’m going to take a closer look at some of the presuppositions underlying movement and perception in early or early-inspired D&D rulebooks. Originally, I was going to make one short post about treating movement rates as a non-random ability score, and then a separate one trying to figure out what different behavior that flashlights would have compared to torches if you were to set your dungeon crawl in the modern age. As it turns out, though, it’s difficult to separate light and movement since they are intertwined in how players perceive and then interact with the game-world.
On 12"-Scale Movement
Defining movement rates in inches seems at first glance a vestige of D&D’s origin in tabletop wargames. Movement rates were given as such in Dungeons & Dragons (“OD&D”, 1974) and Advanced Dungeons & Dragons (“AD&D”, 1977-9). The base rate of movement for an O/AD&D character is 12”. The rate decreases to 9”, 6”, and finally 3” for increasing levels of encumbrance . Being written for literal tabletop play, it should come as no surprise that the maximum move is equivalent to a figure being slid down a twelve-inch ruler. This physical dimension of the game informs the presentation of the game’s mechanics. Why is it said that a character makes two moves per exploration turn, rather than defining the base movement rate as 24”? Rulers don’t come in twenty-four inches. Why are movement rates not divided by 3, to become (4, 3, 2, 1)? You would have to multiply by 3 to move at the anticipated scale of action, tens of feet. The rules are perfectly simple for playing with your figures on a table, where you can expect different scales when fighting, exploring, or waging war. There is no math you need to figure out, no need to refer to different movement rates for different scales. This is the most important reason that dungeon maps are described in squares of 10’ by 10’. They are really being described in literal inches on the table .
The 1977 publication of D&D Basic was written for non-wargamers by admission. It gave movement rates in tens of feet, with an aside that “Since DUNGEONS & DRAGONS was originally written for wargamers who are used to miniature figures, distances are often given in inches” (p. 9). By the 1981 revision (“B/X”), there was no context for why movement rates tended to be perfectly divisible by 30. The OSR tradition of rulebooks etc. has largely followed B/X’s lead. The dungeon crawl game is not often now treated as a tabletop wargame requiring precise rules for movement and scale, and it is not uncommon now anyway to stage the game in one’s imagination where fiddly numbers lead to confusion. The 12” ruler scale is functionally obsolete, and there is nothing wrong with that. The same game is being played, to speak loosely, if only on a different theater that requires different techniques to simulate happenings while minimizing complexity.
Yet there is another benefit to the ruler scale of movement rates, that is, to how the rates range from 3” to 12” for player-characters. On average, one can expect a rate of 9” or 12”. This is the same average range for random ability scores determined by rolling three six-sided dice. Not having an ability score for agility or speed, our hunch is often to treat dexterity as the ability score that modifies speed, or sometimes adding a distinct agility score. Name-brand D&D has historically been much kinder in presuming our characters’ movement rates, ascribing it only to how much they carry and not to some innate speed attribute . Nevertheless, there being an equivalent value for “agility” gives us the benefits of having another heuristic to judge dicey situations without the detriment of keeping yet another individual character score (one modified on the fly by encumbrance, nonetheless). Need to know if the players win out on a chase? Roll less than or equal to the slowest character’s rate, modified by the opponent’s rate if desired (+/- the difference in movement rates). Of course, I made that up, but what would you have done? It’s as easy a tool as are the actual six scores.
On Torches & Flashlights
It is difficult not to discuss rules for light sources outside of the context of movement, since one’s perception informs one’s actions. OD&D actually did not have rules for the duration or effectiveness of different light sources; not barring any prior supplements, rules for light would not be included until AD&D or D&D Basic (1977). In both books, a torch lasted for six turns (basically, a cycle of exploration lasting one hour) and a lantern lasted for twenty-four turns (four cycles/hours). AD&D prescribes the torch as giving off light in a 40’ radius whereas a lantern gives off light in a 30’ radius; D&D Basic would give both a 30’ radius instead. Although I prefer keeping the same radius, there are interesting consequences to both methods. AD&D scales movement in combat to 3’4” (i.e. 1/3 of 10’), such that a movement rate of 12” scales to 40’ or one third the movement rate of underworld exploration. By carrying a lantern, you are inhibiting your character’s vision and thus their capability to move in an encounter. Yet 30’ scales nicely to dungeon exploration, given that the different movement rates (120’, 90’, 60’, 30’) are multiples of it. It is as though your movement rates designates how many segments of movement you can have each turn, where a segment corresponds to being as far away from your original position as possible while still being able to see it.
Understanding how light informs player decisions in this way is important to me in figuring out how more modern light sources should interact with the dungeon crawling game. The most distinctive difference between a torch and a flashlight is that a torch gives off light in a sphere, whereas a flashlight gives off light in a direct beam. This already impacts such things as determining encounter surprise, or even more simply how players interact with the game world. Let’s say that a typical flashlight has 100 lumens or 100 candelas , and so it shines 20 m  away from its wielder, which is equivalent to about 60’. This means that the wielder with a movement rate of 120’ per turn has two segments along the same lines as above. This scales inconveniently with movement rates of 90’ and 30’, so a doubled rate as per OD&D with a total movement per turn of 240’/180’/120’/60’ might serve better.
Nevertheless, when it comes to the long durations for which flashlights last and how much farther they are able to shine, it might be more interesting to introduce new complications into using them (and thus new ways to structure the dungeon game) as opposed to adopting them to the same use cases of torches and lanterns. It’s like introducing firearms into an otherwise early-to-middle medieval wargame; it feels like cheating. First, abstract movement instead of scaled movement may serve flashlights better, even if movement rates on the 12” scale have applications besides literal tabletop play. Gus L and others use a method where moving from one keyed area in a dungeon to another takes one turn, i.e. it costs one encounter check (or hazard die roll) , and there is the possibility that long passages can cost multiple encounter checks to traverse. Second, other resources can be introduced instead of light, including ones with random or inconsistent rates of consumption. Consider drinking water, for example, either by players becoming exhausted as an event on the hazard die without having water (i.e. water bypasses exhaustion), or allowing players to restore hit points on an expedition only by drinking water. Light is still a prerequisite of exploration, but it is not a resource being tracked. Seeing as OD&D does not give durations for light, I could see a resource allowing players to skip rest turns being quite valuable to take on an expedition . Finally, other resources such as hit points could be emphasized.
I have not tried any of these new methods yet, but I cannot imagine they would be hard to give a shot. I would love to hear your ideas on alternative resource management topics besides light, and your thoughts on movement rates versus abstract movement etc.
 Unlike some later OSR games, which leaned fully into resource management being a full-fledged aspect of the game, resources such as torches and rations took up a flat 80 coins (8 lb.) of the character’s carrying capacity regardless of how many torches or burgers etc. that character was holding. The only things that variably factored into a character’s movement rate was combat equipment—i.e. weapons, armor, etc.—and treasure as given in coins and gems. This was mirrored in D&D Basic (1981)’s rates of movement, defined as a function of armor worn and additional weight in coins of other equipment. Although torches were finally given a duration in AD&D and D&D Basic (1977), being able to carry an infinite amount of them made the resultant resource management a game of memory more than a game of management (“Shit, did we forget to buy torches in town?”).
 However, in the AD&D DMG, Gygax recommends always scaling the dungeon at 3" representing 10' due to figurines having large bases, and he also points out that then "This allows typical depiction of the typical array of three figures abreast" (p. 10).
 Dwarves, being short, have a base movement rate of 6” in Chainmail's fantasy supplement. Still, this is much less complicated than having speed attributes for individual characters.
 For no good reason, I did a stupid amount of research about the difference between lumens and candelas and candlepower. Let me summarize how I understand it, and if you know better than me, please correct me: lumens are how much light is coming off of a source, whereas candelas are how that light is diffused from that source depending on what fraction of a sphere the light is passing through.
Think about a flashlight versus a torch; they could have the same number of lumens, but light flows from the flashlight in a beam whereas light flows from the torch in all directions. This means torchlight is much less weaker per lumen than is a flashlight.
Yet 1 candela is said to be the light given off by a candle; you can see that a flashlight requires many less lumens than a candle to illuminate an area to the same degree, but how many lumens does a candle have? The answer is simple, and it relates to how the candela is calculated. The steradian unit is a fraction Ω of a sphere’s surface area A, such that Ω = A/r^2. A sphere has 4π steradians in total because when A = 4πr^2 (the surface area of a sphere), then Ω = 4π. Consequently, a candle has 4π lumens because that is how many lumens it needs to have 1 candela of light, and this is called 1 candlepower. Meanwhile, if we consider a flashlight to have only 1 steradian (1/4π the total surface area of a circle), as is often implicitly considered, then the flashlight has as many candelas as it has lumens. A flashlight of 1 candlepower, i.e. 4π lumens, would have 4π candelas, being 4π times as effective as a candle in a given area.
There is no reason to know any of this.
 To find the “throw” of a flashlight in meters, multiply the number of candelas by four and take the square root. Read more here: https://davestechreviews.com/2020/05/26/converting-candela-to-throw/
 For an analogous situation on the overworld, imagine that keeping rations is a way to bypass a turn of gathering or hunting food when you get hungry.