Bell Curves, Criticals, and the Odds of Doubles on 3 Expanse Dice.

The various AGE (Adventure Game Engine) games from Green Ronin all have the same core mechanic — to see if you succeed at something, roll 3d6, one of which is a “Stunt Die.” Add the 3d6 and any bonus you have, and compare to a target number.

If any two of your dice are doubles (they have the same value), you earn “stunt points,” equal to the value of the stunt die.

In this article, I want to talk a bit about bell curves, critical success systems in RPGs, and  what the odds are you’ll get doubles when your roll 3d6. And I’m using pictures of the Expanse RPG Dice Sets, since they are cool-looking and currently being crowdfunded on Kickstarter.

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So, lemme start with three important notes.

I am NOT the developer for the Expanse RPG. That role is very ably handled by the extremely talented Ian Lemke.

Second, I AM biased in favor of Green Ronin, since they employ me to be the Fantasy AGE developer and I thus benefit (at least indirectly) if their projects make lots of money. So, yes, this post is happening at this time in part so I can highlight this Kickstarter. (But it’s also good game design analysis.