Design Spotlight: d100 Systems

Design Spotlight: d100 Systems
D100 Systems are everywhere. Some big names like Call of Cthulhu (the original Chaosium version) and (one of my personal favorites) Dark Heresy utilize a d100 (or 0-99) dice system for the core of their game.While the d20 system is generally more popular, this week's Design Focus is on d100 systems (aka "d-Percentile Systems")


The How To...
Generally you roll 2d10 with one representing the tens column and one representing the ones column. D100's exist, but generally you can use those two dice for other things. (Like skill/statistic rolls) Dark Heresy even inverts the numbers to determine what part of the body is hit!


"It's Fuzzy Math See?"
D100 systems have a very unique advantage over other dice sizes used for systems. They directly represent percents. Sometimes this is a boon when you are trying to design a system. Instead of relying on an average roll of 4/6 on a d6 to represent the odds "50%/50%" you can actually roll 50% on these dice.

It's nice for both you (the designer) and your players to be able to do quick math (or even no math at all) to figure out your percent chance of success or failure in a given situation. Since This generally makes it easier for younger players/inexperienced people to pick up a system quickly. 100 is easily divisible and most of the population can figured out fractions from 100. This is something d6 systems have a problem with. (For example; the average roll of 2d6 results in a total added value of 7)


Verity in Your Diet
2d10 can generate 100 numbers. (As most D10 have a 0-9 listed) I know this might be a little obvious but it is a overlooked factor. This is generally the highest you can get on today's commonly sold dice. (2d20 would be the highest... but a d40 system would be... unique.) What this means is you have a wider range to assign results. (Don't go crazy with this! It's a double edged sword!) For example: I hear a lot of d20 players complaining about critical misses on a d20 roll of 1. (It's a 1/20 chance to epically both whatever it is you are doing!) Some games fix this with a "confirmation" roll but d100s don't necessarily need that confirmation.


The Flip-Side
-Percents: When someone sees that they only have "33% Strength" it tends to be somewhat of a turn off because they know percents so well. (You might want to phrase it as, "33 Strength Points" or something similar.)
-Fuzzy Math: Sometimes ambiguity is a good thing! The fact that the average player doesn't know you're average damage for 23+6d6 is 44 is sometimes a good thing. They know it's "high" but they generally can't guess even in the ballpark!
-Verity: This is a double edged sword. Adding TOO MUCH can confused players. Keep in mind "Just because you CAN doesn't mean you SHOULD."
-Over 99: A common issue is rolling results (with modifiers normally) over 99%. Sometimes this doesn't make sense to players mind even though your math does. Anything "automatic" tends to be a VERY big deterrent to players. (They like to be engaged!)