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Systems Thinking Chapter 2: Green Slime

There's a problem in your game. At first it's not a big deal, but over time it gets worse and worse. Not only that, it gets worse faster and faster. The probable cause is a reinforcing loop or, as I like to call it, green slime.

As a graph, this is what a reinforcing loop green slime looks like:

The vertical axis could be all kinds of things. In graph 1 it might be player dis-satisfaction. In graph 2 it might be game challenge. The point is that the problem gets worse over time exponentially.

Here's the green slime loop as a generic system diagram:

Performance is some measurable quality (not necessarily quantifiable), such as player satisfaction.

Consequences are what happens as performance changes.

Growth Action is an action or requirement that drives the loop, usually a rule or maybe a behavior.

Performance Drive/Action Consequences is simply how this action reinforces the performance change.

THIS IS ONLY AN ILLUSTRATION. It's meant to give a generic idea of how the loop functions. It's not a template into which you can plug bits of your game and get a magic result!

Actual Play Example

This isn't a great example, but it's the best one I can think of right now.

When my friends and I were relatively new to RPGs, we achieved the impressive coup of getting my older brother to play with us. A buddy of mine GMed a pretty standard D&D adventure. The GM wasn't sure how to determine what monsters to put us up against, so he went through the Monster Manual and looked for monster whose combat damage was low enough that even if the monsters did maximum damage, it would take two hits to kill us. The monsters were underpowered, and the players started to get bored and restless. In an effort to fix the problem, he upped the number of monsters. Instead of 4 goblins, there were 6, and then 8. Combat took longer, but the monsters still weren't able to actually threaten the survival of the characters. This made the players even more bored and annoyed. Eventually, my brother suggested a better foe for us: an ettin. "But that can kill you in one hit!" the GM objected. "Exactly" was the response. The GM relented and we had a close combat where a couple of characters almost died. Everyone had fun.

The problem was the GM's unstated rules of "use monsters that need two maximum damage hits to kill the PCs". This was a perfectly reasonable action to take in a game system that provided a large number of monsters, but no rules for matching them to the strength of the characters. Here is that situation as a system diagram:

In this case, the solution was to discard the ad-hoc rule that was reinforcing the loop and increasing player boredom.

The point of the whole systems exercise was to identify the issue so that you can work towards a solution. In this case, the more experienced player (my brother), could see the trap the GM was falling into and use his own experience, or perhaps his own ad-hoc rules to suggest a better solution.

You might have noticed that this loop was also a symptom of a lack in the larger game system. In this case, it's likely that more problems would crop up later in the campaign because there's still a bigger root problem to be tackled. Figuring that out is part of systems thinking too. Hopefully we'll get to talk about identifying larger systems issues later on.

Can anyone suggest a better example of a reinforcing loop? Anyone have an example of a case where a reinforcing loop has a positive impact on gameplay, rather than negative? PLEASE COMMENT even if it's just to say you think this is a load of bunk. I really want to hear if anyone else is finding this as helpful as I am.


I think you should've kept the footnote about green slime.

Heh. As soon as I saw I'd published by accident instead of saving as draft, I knew you'd catch me.

Green slime. Stupidest. Monster. Ever.

Have to idsagree on one MAJOR point - there are many stupider monsters than green slime.

The feedback loop is good. One example of this being used as a positive motivator would be in game rewards for character play.

performance is player satisfaction. As performance changes - in this case an increase in character play, it leads to a growth action, which is an increase in experience points, which then reinforces the player and the others to increase their level of play, to get more experience etc.

I think that to solve a game problem you might want to find ways to take the negative problem loop that you are referring to and turn it into a positive feedback loop. Players, and people in general, respond much better to positive reinforcement.

Do you remember the 'death spiral' phenomenon of some of the D&D optional rules? This is where as you get injured, your ability to fight or use skills decreases, which means you get more injured, so you get less effective, etc. The green slime loop sort of reminds me of that, but on a system scale.

IS any of this maing sense Tony?

Yes, the "death spiral" is an excellent example. In fact it's better than mine because it's an actual rules mechanics example where mine is actually an undocumented practice (if that makes sense).

Good point about the positive feedback loop. In fact any time players increase in some area of performance in response to an XP reward, that's a reinforcing loop.

And I'm sorry. Green slime? All it does is drip. Then you die because you forgot to check for green slime. Then you turn into green slime so you can slime the next party of adventurers. Pretty soon you've got a whole campaign world swimming in green slime.

What a great premise for a campaign. Most of the world has been changed into slimes and oozes. Only a few people that are paranoid and constantly checking the ceiling have managed to survive. Jubilex and his demonic and demon-worshipping follers continually hunt the last remaining humans and demi-humans. Who can save the world from this terrible fate?

The adventurers of course - Armed with their paranoid dungeon crawling skills.

Now you've got to admit that makes them a better choice for a monster than rot grubs or violet shreikers, or flightless birds.

Man, green slime would be a serious terror weapon in a D&D world. Load up the catapults, baby.

Awesomeness. I have been pimping the Systems Thinking page (http://www.systems-thinking.org/) for a while on Forge and stuff and hoping someone could make good use of it. You recommend the book?

Riddle of Steel's SAs, when played Blood Opera style definitely create a positive feedback loop. I think immediate rewards in general work that way.

Tangential D&D monster note- there was some kind low level demon that regenerated everything except holy damage- I thought, what happens if you drop a few of those into a Gelatinous Cube and let it keep devouring them as they regenerate?

For a few hundred years? Gelatinous Cube War! Each is 5 tons, silent except for the debris they push, and never gets tired. A slow bulldoze of never-ending cubes crushing castle walls!

Silly, but fun.

The book is quite thick and has several sections beyond systems thinking. Since they deal with group dynamics and improving performance and communication of groups they MIGHT be extremely useful to role-players. I haven't delved very deeply yet, so I can't really judge. I found the systems thinking section to be a great overview of the field. I'll check out that page. I'm new to this whole thing, so I have a lot to learn yet.

Ear seekers, throat leeches, green slime, yellow mold, and rot grubs (almost forgot the rot grubs) - the classic cheap ways to kill characters.

But for "stupidest monster ever published as a serious inclusion in an official product," it's really tough to beat stwingers.

ok, phil, I'll bite - what is a stwinger?

A stwinger is the lamest fairy ever to be misbegotten out of some damn fool gamer's imagination. The one thing that stwingers most enjoy is swinging from beards, dwarven beards in particular (as those are generally full and long). So the stwinger uses its powers to charm the dwarf into standing still, and then swings from its beard, doing subdual damage, until the dwarf reaches 0 hp and falls over. Thus deprived of its amusement, the stwinger wanders off elsewhere.

This miserable excuse for a "monster" was published in the "Fiend Folio" supplement (MC14) to the second-edition AD&D Monstrous Compendium, the looseleaf binder version - thus carrying on the noble tradition of the Fiend Folio offering some of the stupidest and utterly worthless monsters for all of D&D.

Worse, I've just Googled "stwinger" and discovered some fool converted stwingers to third edition. The mind boggles.

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