Daily D&D Ramble: What if Primes were important?

I made it to CO safely, if loopy. I spent the day with family, playing games and catching up. Hopefully tomorrow’s will be done earlier, with planning and stuff. I did a lot of thinking on the drive. One of my thought may be a little useless, but I’m going to share it anyway!

So I had a loopy thought, where if a player wanted to try something impossible, I’d let it happen if he rolled a prime number. And he could roll whatever modifier he wanted. What would the odds of that be? And so I got curious and we’re going to look at the die sizes in turn. We’re also going to use the range -1 to +5 for modifiers, as that’s the range that 5e normally has. And I’m going to touch advantage in this at all, as I’ve been up for a stupid amount of the last 2 days. Like 40 hours out of 48. Also we have to leave some work as an assignment for the pupil :p

I was going to write out things for it, but its just going to be pretty lists of numbers, so I’ll just get the data out of the way. I ws also going to highlight primes, but that’s a lot of work I am not capable of doing tonight. If needed, let me know and I’ll do it later.

D2 (1, 2):50%
-1:(0,1):0%
+1:(2,3):100%
+2:(3,4):50%
+3:(4,5):50%
+4:(5,6):50%
+5:(6,7):50%

D4 (1, 2,3,4):50%
-1:(0,1,2,3):50%
+1:(2,3,4,5):75%
+2:(3,4,5,6):50%
+3:(4,5,6,7):50%
+4:(5,6,7,8):50%
+5:(6,7,8,9):25%

D6 (1, 2,3,4,5,6):50%
-1:(0,1,2,3,4,5):50%
+1:(2,3,4,5,6,7):66%
+2:(3,4,5,6,7,8):50%
+3:(4,5,6,7,8,9):33%
+4:(5,6,7,8,9,10):33%
+5:(6,7,8,9,10,11):33%

D8 (1, 2,3,4,5,6,7,8):50%
-1:(0,1,2,3,4,5,6,7):50%
+1:(2,3,4,5,6,7,8,9):50%
+2:(3,4,5,6,7,8,9,10):37.5%
+3:(4,5,6,7,8,9,10,11):37.5%
+4:(5,6,7,8,9,10,11,12):37.5%
+5:(6,7,8,9,10,11,12,13):37.5%

D10 (1, 2,3,4,5,6,7,8,9,10):40%
-1:(0,1,2,3,4,5,6,7,8,9):40%
+1:(2,3,4,5,6,7,8,9,10,11):50%
+2:(3,4,5,6,7,8,9,10,11,12):40%
+3:(4,5,6,7,8,9,10,11,12,13):40%
+4:(5,6,7,8,9,10,11,12,13,14):40%
+5:(6,7,8,9,10,11,12,13,14,15):30%

D12 (1, 2,3,4,5,6,7,8,9,10,11,12):42%
-1:(0,1,2,3,4,5,6,7,8,9,10,11):42%
+1:(2,3,4,5,6,7,8,9,10,11,12,13):50%
+2:(3,4,5,6,7,8,9,10,11,12,13,14):42%
+3:(4,5,6,7,8,9,10,11,12,13,14,15):33%
+4:(5,6,7,8,9,10,11,12,13,14,15,16):33%
+5:(6,7,8,9,10,11,12,13,14,15,16,17):33%

D20 (1, 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20):40%
-1:(0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19):40%
+1:(2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21):40%
+2:(3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22):35%
+3:(4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23):35%
+4:(5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24):35%
+5:(6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25):30%

I’m not going to write out d100. +0:25%, -1:25%,+1:26%, +2:25%,+3:25%,+4:25%,+5:24%

Okay, the first thing I notice is D2 is out. No one flips coins too often in D&D and its way to easy to game the prime/not prime system. And I think making the player hope for a non-prime bay be a better system. That lets the player win more often. Using D4s and D6s also have some wonky math, but, if you’re using the d8 or higher, the higher your modifier the better your odds of non-primeness.

I don’t have any reason to use this system. I just thought it might be interesting. Maybe I’ll make a system for it. Being unsure whether you succeeded or not if its a high number or having a chance if its a low number is an interesting concept for a mechanic. It makes it more math heavy and requires you to know your primes. The D100 and the D20 may be too much. I dunno.

I could see tying this into some magic system to see if the spell went off wrong. Too much or too little power can mess with things sometimes.

If I was clever, I would have made some spreadsheet or something to make all that above easier to peruse and reuse sometime when I’m more cognizant. But that’s a tomorrow thing.

Cheers!

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