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Back in the day what particular die expression your game used was such a sticking point because that was all we had. The games looked pretty much the same except that some used 1d100, some used 3d6, some used 10d10, some used 1d20 etc. These days there are a lot more nuance to system than just this basic question.
Just as a bit of game design basics for posterity, even though your game definitely shouldnât start or end here, letâs bring out this old chestnut for one more go on the merry-go-round.
It is an oft repeated myth, maybe less so these days, that linear die rolls, such as 1d100 or 1d20, are more âswingyâ than curve style die rolls, such as 3d6.
3d6 is basically a 1d216 â the three dice can fall in one of 216 different ways. Thatâs as swingy as they go. 2d6 is equivalent to 1d36âthere are thirty-six different outcomes (for example one way to get 2, two ways to get 3 and so on).
Letâs take rolling 10 or lower as an example. On 1d20 and on 3d6 itâs both 50%. Same swinginess.
Or letâs say you want something thatâs got 75% chance of happening. Thereâs no exact equivalent on 3d6 but rolling 12 or lower is close, at 74% and change. Of course on 1d20 itâs rolling 15 or lower.
Games like Cthulhu Dark, Fudge and Shadespire use dice curves well. They have wellâthought-out math where you can get rare events (like the 1-in-81 chance of rolling all pluses in Fudge, or the slowly decreasing Insight once youâve started âsupressing knowledgeâ in Cthulhu Dark) but not have to deal with a bunch of adding or comparing big numbers.
Damage die in D&D is an example. 7 damage is meaningfully different than 4 damage than 1 damage because they all can kill different monsters.
Another example is rolling on a random table. Entry 7 is 3d6 wolves, entry 4 is 2 grumpy owlboars. Even the 3d6 wolves are different than 1d20 wolves.
When summing and counting up the number of wolves is an example where 1d20 is more swingy than 3d6.
The âmythâ comes from a bad DM practice that was common in the past: to ascribe semantics to the natural die roll. A 4 or 3 was shameful, a 2 was banana-peelâslippingly ridiculous, a 17 or 18 was godlike elegance. The mod on the character sheet didnât really matter, the al-mighty linear d20 ruled all. I can definitely understand why a lot of players would have a lot of lingering resentment towards linear after being subjected this!
If you try to be all â+1 from the rain, +3 from the vegetation here, -2 for the exhaustionâ on 4d3 (as per Fudge) you are in for a world of trouble. A net change of -2 take your chances of succeeding from 62% to just 19, in the typical case.
In curve systems, modifiers make more of a difference near the middle of the curve. A terrible or superb character in Fudge is less affected than someone near the middle of the pack, who can get completely messed up by a mod of -1 or -2.
This can sometimes be what you want, but, you are not getting transparent probabilities and youâre liable to mess up. A game like Burning Wheel where the difference between Ob2 and Ob3 differs wildly depending on amount of dice in the pool, for example.
A game thatâs consistently using linear, like â this, ²ââ that, or a d20 or a d100 or a d10 or whatever, will map to your players intuition of their odds reasonably well.
I know that enfranchised GURPS players know that they have 50% chance rolling 10 or lower on 3d6 but 75% rolling 12 or lower, but, many more casual players donât know that and Iâd like them to enjoy games too, which is why I suggest linear instead.
âŚyou want a liâl of column A and a liâl of column B. Good luck my friendsâĽď¸