Specifically, I'm talking about how D&D 5th ed handles the challenge level for encounters.
The short and quick of it is the DMG for D&D 5th ed has an algorithm inside it for computing encounter difficulty. Essentially, every PC - based on their character level - has an XP threshold for an Easy, Moderate, Hard, and Deadly encounter. When you add up all those thresholds (inside one group) across the party, you get the party's threshold for those encounters. That XP then gives you a budget to buy monsters with (with modifiers for how many monsters you are fielding). The only catch is, monsters also have a "Challenge Rating" which is less of a CR as it is a "your PCs must be at least this level to enjoy this ride." Why? Because even though a monster's XP value might mean it is only a "moderate" encounter for your group based on thresholds, the power level expected in its stats means it might one shot one or two people. (For example, a Black Dragon Wyrmling is a CR2, but its breath weapon will one shot everyone it hits that isn't a fighter with a Con above 13, regardless of whether or not they make the saving throw.)
Table Top War Games
This algorithm does something cool. It makes filling your adventure kind of like preparing an army list for a table top war game like 40k. You have 400 points for this encounter, and goblins cost 25 a pop. However, when you buy 8 goblins (200 xp worth) it doubles their XP value for challenge rating, and so now that encounter is full with a fight that will give your PCs a
It also lets you plan out your adventure's pacing and difficulty curve. For example, for the adventure I ran on Saturday I wanted a deadly encounter to finish things off, a couple hard, a couple easy, and a moderate encounter. I worked out how many of each added up to the totla XP I wanted my group to face (I wanted them level 3 by the end) and then went shopping. What could have taken several hours of research and prep thus only took about 25 minutes, complete with having alternative lists for if I had 5 PCs or 6 PCs show up (each of which increased the various thresholds and also XP demands to reach level 3 by the end.)
Why I Like This
While I didn't partake of it per se this Saturday, I like this because by automating so much of the mechanical part of prep-work (the DMG even has some pre-gen maps you can use) I was freed up to work out the story particulars for the game and a few other touches. Like I said, I didn't go nuts with this on Saturday, my prep-time was kind of short for that, but what time it did give me made the adventure more fun and unique. I got to use dragons and kobolds instead of something more standard (I can hear some of you laughing at me for saying kobolds aren't standard :P ) like goblins or whatever.
It is being used more as I prepare for the next session where I'm hoping for more plot, more story, and more RP to go in along with the combat that happens.
What I've Learned
The big take away for me from this comes in the adventure preparation. I'm more used to having the story then working out the demands for the story into the adventure. With D&D I'm doing the opposite. I'm building the mechanical encounters, and then filling in the details around them. It makes for an interesting way of adventure prep, and I may have to give it a try in my Star Wars game coming up in the near future.
Either way, it is just fun seeing a different way of doing prep and how well it can work.