For an RPG resolution mechanic, I like coin pools. I like that it is open-ended on the high end. i.e. There’s no upper limit on the scores that determine how many coins are in the pool. I like that it has diminishing returns. i.e. Each coin added to the pool increases the probability of success by a smaller increment than the previous coin.
What I don’t like is that the increments still seem a bit too big.
To get smaller increments, what if the chance of failure equals the reciprocal of the score? e.g. A score of 4 would grant a 1/4th chance of failure. Thus, a 3/4 chance of success.
OK. I like those numbers better, but how do we do this with dice?
One way is to roll a die with a number of sides equal to the score being used. Anything except a 1 means success.
And you thought people complained a lot about DCC using d3, d5, d7, etc.
It’s really not that bad, though. Just choose the next bigger die you have and reroll results higher than the score. e.g. For a score of 5, roll a d6. 1 = failure; 2 to 5 = success; 6 = reroll.
It gets a bit annoying for scores between 12 and 20. At 13, if you’re rolling a d20 and rerolling 14s and above, you’ll be rerolling 35% of the time. Having a d14 and d16 helps out. A d24 and a d30 help for scores over 20. Over 30 starts calling for some creative solutions. At 30, though, we’re up to a 96.7% chance of success, and 2 to 30 is a decent range for scores. Probably more than is really needed.
Alternatively, you could use drawing chits or cards or stones. Put a number of stones equal to the score in a bag. One of them should be a different color than the rest. Draw out the odd stone and it’s a failure.
Any other method?