Double Feature: Encumbrance & Metric Movement

How’s it go, again? “Same song, different chorus”?

My friend mv of hypertext corner wrote a great article about introducing novel uses and consequences to light sources in Mothership [1]. We had been talking about it since I wrote my article about how rules for light sources in Dungeons & Dragons relate to character movement insofar as a character sees much less farther than they can walk in a turn [2]. Their solution is since flashlights shine much farther than a character can presumably walk in a turn, it would be more interesting to think about how directional light informs encounter surprise. It sounds really fun!

During our conversation, though, we were also talking about rates of exploration in Mothership which, by the book, aren’t given. We talked about it quite a bit before realizing it didn’t matter in the scope of mv’s article. They told me that characters had a movement rate of about 10-15 m and so I was like, okay, maybe we can extrapolate that the exploration rate is 30 m maximum since that’s the length of a metric ruler [3]? Maybe you can work with three movement rates instead of four, from 30 m to 20 m to 10 m, and divide by two for encounters? Ugh!

So none of that was relevant to mv’s article, but I decided I would write on making a physical tabletop movement system for metric distances. The problem is that I made assumptions that weren’t in Mothership at all and are not presuppositions held by the Mothership community of players at all. These assumptions were made with respect to the role that encumbrance played in Mothership, which to my understanding doesn’t have an encumbrance system. In their post about ‘dungeon’ crawl procedures adapted to Mothership [4], mv recommends quadra’s encumbrance house rule for the game which is less an encumbrance system than an inventory one [5]. Characters do not become encumbered the more they carry; they only have a set number of item slots based on their STR score.

This doesn’t mean that quadra’s encumbrance house rule isn’t good or useful, but I carry a different set of presuppositions about how a creepy crawly game should go that informed how I thought movement rates in Mothership should work. Regardless of which presuppositions work best for Mothership in particular, I wanted to discuss the mathematics behind combining two things such as character inventory and movement rates. Then, I wanted to discuss a metric movement system that presupposes an encumbrance system where characters move more slowly the more things they carry. None of this hinges on Mothership per se, but Mothership and its surrounding culture serves as a reference point for this article, and I think then this article might be useful for Mothership if you share some of its same presuppositions.


The house rule for encumbrance suggested by quadra is as follows:

Player characters can carry a number of items equal to their Strength/10, plus 1 per hand, plus whatever they’re wearing, within reason (so a vaccsuit with magboots and a bodycam won’t count towards this). Items stack 3/slot.

As I said in the introduction, this rule is not really one for encumbrance as much as it is for inventory since the character is not becoming encumbered. There is nothing wrong with this at all! In fact, for a game like Mothership which is not necessarily about stuffing your pockets full of coins, an inventory system that focuses solely on what your character has on their body is really useful. I just want to acknowledge that this rule seems to work really well for what it seeks to accomplish, so none of what follows should be taken as a rebuttal to it. It is only an investigation of what things could possibly factor into an encumbrance system where what you carry makes you slower.

When it comes to paper and pencil, our brains are limited by our ability to find and process information. Anything that requires putting more than two and two together is a chore. Character sheets can do a lot of heavy lifting by making it easier to store information for future reference, but often I don’t even want to have a character sheet full of information just to play a game.

It’s for this reason that out of many of the rulebooks I’ve read, I think that not many have surpassed the original Dungeons & Dragons with respect to maximizing the consequences of encumbrance for minimal mathematics. Your character can carry a certain number of pounds (actually, coins, each being 1/10 lb.) before slowing down in increments of 3". The function for items carried to movement rate is as follows:

  • 0-75 lb. → 12"
  • 76-100 lb. → 9"
  • 101-150 lb. → 6"
  • 151-300 lb. → 3"

The only piece of information you really need is the total weight of the things that your character is carrying.

The temptation for many games coming out of this same ‘school of thought’ is that it would be nice for either carrying capacity or movement rate or both to be functions of an individual character’s ability scores. This would be fine if these things didn’t interact, but consider any old D&D where what you carry slows down your movement rate. By making both factors vary on an individual level, you make it very difficult to make an intuitive function that accepts a character’s carrying capacity and their base movement rate as inputs.

Let’s suppose encumbrance in Mothership is a function of a character’s STR and it has levels of granularity. For example, we can say for every STR / 10 items carried besides what is in one’s hands (borrowing quadra’s formula), the character is encumbered by that many degrees up to 2. If movement decreases by thirds, it is easy to map encumbrance to movement rates:

  • 1 × STR / 10 + 2 → 30 m
  • 2 × STR / 10 + 2 → 20 m
  • 3 × STR / 10 + 2 → 10 m

However, if the third column has to be computed as a function of one’s SPD, there is double the complexity to determine one’s movement rate, especially considering different rates for exploration and encounters.

  • 1 × STR / 10 + 2 → SPD × 3 / 3
  • 2 × STR / 10 + 2 → SPD × 2 / 3
  • 3 × STR / 10 + 2 → SPD × 1 / 3

This is not as complicated for one degree of encumbrance, which we can suppose halves speed.

  • 1 × STR / 10 + 2 → SPD × 2 / 2
  • 2 × STR / 10 + 2 → SPD × 1 / 2

Still, you can see how the function to determine one’s movement rate becomes very complicated when it involves two variables that are specific to character’s ability scores. You could get away with picking one for some level of character specificity, but don’t get carried away!

I myself would prefer treating item slots and speed as constants, not character-specific variables. Suppose you gain 1 encumbrance for carrying 4-6 item slots on your back, and then you gain 1 encumbrance for wearing heavy armor. Although treating armor separately adds another factor, both it and carrying 4-6 item slots are binary yes/no (i.e. 1 or 0) factors. You just add those binary factors for some encumbrance 0-2.

  • 0-3 items, reg. armor → 0 → 30 m
  • 0-3 items, heavy armor → 1 → 20 m
  • 4-6 items, reg. armor → 1 → 20 m
  • 4-6 items, heavy armor → 2 → 10 m

Alternatively, say that a character gains encumbrance for every 3 items carried beyond 3, up to 9, and that heavy armor takes up 3 slots. These are the same, and it allows characters not wearing heavy armor to carry something else instead.

  • 0-3 items → 30 m
  • 4-6 items → 20 m
  • 7-9 items → 10 m

It should be said, though, that this scheme only matters if you want movement to be a function of encumbrance at all, rather than having a simple “this is how many things you can carry” rule going on. You can just see how the math stacks up when you have two variables in a paper-and-pencil function.

Going forward for my metric movement system, I’m going to assume an encumbrance system with zero to two levels of encumbrance for characters so that movement can be easily divided into thirds along the lines above (30/20/10).

Metric Movement

I feel like movement rates for rulesets that use metric measurements like Mothership does have not really been dealt with in depth. The zine edition of Mothership (“0e”) says that in a combat round, characters move a number of meters equal to their SPD / 2. On average, this is a rate of 16 m per combat round. It can be halved if the character is wearing heavy armor and fails at a Strength check while moving.

The forthcoming box edition (“1e”) instead has players use range bands for movement and distance. This has been a pretty common solution for handling finicky movement rates, especially during the transition from tabletop play to digital play (or even just theater of the mind). A range band is a relative description of distance between two things. Mothership 1e has four: close, nearby, far away, and out of range. Range bands are useful because they are casual descriptions of how far two things are away from each other. However, they are mostly useful for judging whether one character is in the reach or range of another character trying to attack them. I can’t wrap my brain around a map of characters whose distances between themselves are all given relatively.

So, if you want to play Mothership or any other crawly game using metric measurements, this is for you!

Variable Base Movement Rates

The average value for a character’s SPD score in Mothership is 33, resulting in a combat movement rate or 33 / 2 ≈ 16 m per round in 0e. This is pretty fine! You could say that the movement rate for exploration is equal to a number of meters equal to the character’s SPD score, no division or multiplication necessary. It’s nice to be able to use ability scores directly wherever possible if the ability score has one such primary use. Then, it’s not difficult to say that the combat rate of movement is half that of the exploration rate of movement. This is great if movement speeds aren’t expected to be modified further.

The main detriment of a variable movement rate is that it is difficult to modify with respect to more than one factor, e.g. in this case explorations versus encounters. Suppose that characters can be encumbered by certain degrees, say from zero to one. By what amount should one degree of encumbrance impair movement speed? Now, given a variable movement rate, we need to calculate different rates based on context and on encumbrance all derived from a variable score from 6 to 60. Perhaps one degree of encumbrance impairs movement rates by a half, such that the exploration rate becomes SPD/2 and the combat rate SPD/4. This is fine, but it is not very granular.

How about zero to two degrees of encumbrance, each one reducing rates by a third of their maximum value? This requires a bit more math, and would be complicated to figure out on the fly. An average SPD becomes exploration rates of 33/22/11 m, and encounter rates of 16/11/5 m. Perhaps the math is not the worst if you calculate these values upfront or if there were a table for them, but a black box function is not any more desirable to me than is doing math whenever you carry one thing too many. This to me is the issue with having variable character-specific movement rates. The equivalent would be D&D having a variable speed score of from 3-18 that decreases by a fourth per degree of encumbrance. Moreover, it’s just not as useful for exploration.

Constant Base Movement Rates

What if Mothership instead had constant base movement rates like D&D? In my previous post [1], I discussed how D&D’s movement rates are intended for use with foot-long rulers of twelve inches. This is why a character’s base movement is 120’ (12”), and it decreases to 90’/60’/30’ with varying degrees of encumbrance.

A metric scale of movement might take inspiration instead from a 30 cm ruler. So, given Mothership, why not assume everyone has a virtual SPD score of 30? Given zero to two degrees of encumbrance, exploration rates can be 30/20/10 m and encounter rates 15/10/5 m (for which you can also use a 15 cm ruler). Not having to account for variable SPD scores and instead assuming the same base rate for all characters, we can get away with more granularity for characters and also be able to scale movement to a household tool of measurement. You may even need only specify exploration movement rates, and say in the context of encounters that they are halved.

The main issue with literal movement rates, as Mothership 1e points out, is that they are finicky for games staged in the imagination of its participants. A ruler is very useful for tabletops, but you don’t have a ruler in your brain. What good are numbers then? In such a case, mv has already developed a heuristic for abstract movement based on how many hazard die rolls are made to traverse from point A to B [4]. This method is very common for what Gus L calls neo-classical play since besides reducing bookkeeping for time and encapsulating a whole set of dungeon crawling outcomes, it is much easier to understand imaginative movement abstractly room-by-room than through vestigial tabletop wargame numbers [6]. Nevertheless, if you find range bands difficult to wrap your brain around, or if you want to play Mothership on a tabletop with figures and rulers, I hope this is useful!




[3] I owe this knowledge to mv, who hails from the distant land of Europe.





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