kieza
2015-04-11, 03:21 PM
So, I'm working on a system which uses "2d10, roll to match or beat a target number" as its core mechanic. I'm also using a mechanic based on 5e's advantage and disadvantage:
For every advantage (flanking, surprise, higher ground, etc.) you have on a core roll, you roll one extra d10, and discard the lowest. So, with one advantage, you roll 3d10 and drop the lowest. With two advantages, you roll 4d10 and drop the two lowest.
Disadvantage (attacking someone with cover, attacking while prone, etc.) works the opposite way. For every disadvantage, you roll one extra d10 and discard the highest.
Now, this combination does three things that I like:
--2d10 gives you a bell curve, so that average rolls are more probable than very high or very low rolls. This makes skill a larger factor than chance in most circumstances.
--It provides a simple mechanic for handling an advantage or disadvantage: this means less adding up bonuses, and keeps play from bogging down as you add up a half-dozen small, situational modifiers.
--Everyone likes rolling lots of dice.
--And, since I'm using 2d10 as the core mechanic, "roll one more d10, discard highest/lowest" works much better than "roll 2d10 twice, pick the higher/lower result." (I considered copying 5e's advantage/disadvantage completely, but then I realized that you couldn't roll 4d10 at once unless you had your d10's in color-coded pairs.)
But, I've found one frustrating side effect:
If you have advantage and disadvantage on the same roll, meaning that you roll 4d10 and discard the highest and lowest dice, the probability distribution has the same average as an unmodified roll (2d10). This is good--the advantage and disadvantage cancel each other out that way. But--if you have advantage and disadvantage, it makes the standard deviation of the distribution smaller, meaning that very high and very low rolls are less likely. In particular, it makes a critical hit (natural 18-20) or critical failure (natural 2-4) far less likely.
So, my questions to the playground:
1) Is this a problem at all? As players or DMs, would you find it strange/bad that when you have equal advantage and disadvantage, your rolls have the same average as if you had no advantage/disadvantage, but you're unlikely to get a critical hit/failure?
2) Would it be a better idea for advantage and disadvantage to just cancel each other out? That is, if you have two advantages and one disadvantage, should you just roll 3d10 and drop the lowest, like you had only one advantage?
3) If you think it's a problem and you think that cancelling advantage and disadvantage is a bad idea, can you suggest an alternative critical hit/failure mechanic? I'd prefer something where advantage makes critical hits more likely, disadvantage makes critical hits less likely, and having an equal number of advantages and disadvantages doesn't change critical hit chance.
Oh, and for those interested, here's the Anydice code I was using to examine this mechanic:
output [highest 1 of 2d20]
output 2d10
output [highest 2 of 3d10]
output [highest 2 of 4d10]
output [lowest 2 of 3d10]
output [lowest 2 of 4d10]
output [middle 2 of 4d10]
For every advantage (flanking, surprise, higher ground, etc.) you have on a core roll, you roll one extra d10, and discard the lowest. So, with one advantage, you roll 3d10 and drop the lowest. With two advantages, you roll 4d10 and drop the two lowest.
Disadvantage (attacking someone with cover, attacking while prone, etc.) works the opposite way. For every disadvantage, you roll one extra d10 and discard the highest.
Now, this combination does three things that I like:
--2d10 gives you a bell curve, so that average rolls are more probable than very high or very low rolls. This makes skill a larger factor than chance in most circumstances.
--It provides a simple mechanic for handling an advantage or disadvantage: this means less adding up bonuses, and keeps play from bogging down as you add up a half-dozen small, situational modifiers.
--Everyone likes rolling lots of dice.
--And, since I'm using 2d10 as the core mechanic, "roll one more d10, discard highest/lowest" works much better than "roll 2d10 twice, pick the higher/lower result." (I considered copying 5e's advantage/disadvantage completely, but then I realized that you couldn't roll 4d10 at once unless you had your d10's in color-coded pairs.)
But, I've found one frustrating side effect:
If you have advantage and disadvantage on the same roll, meaning that you roll 4d10 and discard the highest and lowest dice, the probability distribution has the same average as an unmodified roll (2d10). This is good--the advantage and disadvantage cancel each other out that way. But--if you have advantage and disadvantage, it makes the standard deviation of the distribution smaller, meaning that very high and very low rolls are less likely. In particular, it makes a critical hit (natural 18-20) or critical failure (natural 2-4) far less likely.
So, my questions to the playground:
1) Is this a problem at all? As players or DMs, would you find it strange/bad that when you have equal advantage and disadvantage, your rolls have the same average as if you had no advantage/disadvantage, but you're unlikely to get a critical hit/failure?
2) Would it be a better idea for advantage and disadvantage to just cancel each other out? That is, if you have two advantages and one disadvantage, should you just roll 3d10 and drop the lowest, like you had only one advantage?
3) If you think it's a problem and you think that cancelling advantage and disadvantage is a bad idea, can you suggest an alternative critical hit/failure mechanic? I'd prefer something where advantage makes critical hits more likely, disadvantage makes critical hits less likely, and having an equal number of advantages and disadvantages doesn't change critical hit chance.
Oh, and for those interested, here's the Anydice code I was using to examine this mechanic:
output [highest 1 of 2d20]
output 2d10
output [highest 2 of 3d10]
output [highest 2 of 4d10]
output [lowest 2 of 3d10]
output [lowest 2 of 4d10]
output [middle 2 of 4d10]