Diceless Fate/Fudge Mechanic for RPG

If you have one hand, you could secretly extend a portion of your fingers. She does the same. Any that match (you both are extending your index finger) counts as a +. Hard to have minus or blank with that.

Your ratio idea could work with some modification. What about picking a "bad" number and a "good" number. Hitting the good number is really good, hitting the bad number is really bad, and falling between them or being on opposite sides is neutral. If it's 1 to 10, you could pick 5 as bad and 9 as good. If she chooses 5 it's really bad, 9 it's really good, 8 or 10 are pretty good, 6, 7, 4, and 3, are pretty bad; and 1,2 are neutral. It's a little bit fuzzy with how you shade the region between the bad and the good number so that needs some work. (For instance I made 7 bad - it's halfway between them but still a little too close to the bad number for my liking) But you only have to remember 2 numbers and you might get the gradiation you are looking for.

Yeah, I'm also not sure I understand why she's not rolling the dice... hahaha I'm sure there's a good reason, though.

I think you've hit the wall in terms of what's possible without physical components. You've handled it very well so far, but anything we come up with would probably just be a variation on that theme -- you think of something, and she tries to guess.

Of course you could embrace those variations -- numbers, letters, colors, farm animals, heck, even sports trivia! If she can guess who hit the game-winning homerun to win the 1993 World Series, her black arrow hits Smaug in the sweet spot!

I'll keep thinking, and will return to save the day if I think of anything. I'm 3 sessions into a two-player GM-less RPG campaign right now, and I had to work out many unanswered questions about circumventing the established system, so I feel your pain!

P.S. Anyone who can answer that trivia question without using the internet gets a cookie. Not from me, though, so don't ask.

Make the wheel with having six (6) values: 2x Blank, 2x "-" and 2x "+".

That's an even easier option... Great input Ramon!

TL;DR - What follows is long winded way of "Each pick a number in a range and subtract them, see if the result is lower than an ability score"

Do you want the + and - of the FATE system because it also includes a degree of success or failure, or perhaps because of the bell curve the multiple dice provide?

I love the benefit of fudge/fate that it averages out to 2/3 of the rolls are within 1 of your skill level, with a nice bell curve away from it.

Here's a nice table from Fudge dice probability tables n is the dice roll, P(n) is the number of combinations of those rolls that end up with that result, P(n-) is the % chance of rolling that number or LOWER, and P(n+) is the % chance of rolling that number or HIGHER.

Look at that sweet, sweet curve.

The system you're using now is great - so it makes a good base to change in order to get the bits the Fate/Fudge dice give.

1. The non-linear curve of results
2. Player ability scores
3. Degree of success or failure?

Okay,It's not hard to replicate a semblance of this -

1. Your sister will have an ability score from 1 to 5 (really, a 5 is dramatically better)
2. I don't think you need to replicate both sides of the curve; just having a curve at all is enough. So we'll do this: each of you chose a number between 1 and 6 and subtract them (always greater-lesser to get only positive numbers).
3. Any result LESS than your sister's ability score is a success. A perfect match = success with a bonus. Equal to the ability score = success at a cost (like FATE), and greater than the ability score = failure.

You can adjust your sister's ability score based on the difficulty of the task. Or you could, if you wish, make "harder" tasks pick from a larger range, like you do now (a harder task you would both pick between 1 and 10, for instance).

This will give you a curve rewarding precision, as there are dramatically fewer numbers further away from 0. Also a use of ability scores that provides the range of precision she'd need to be successful. You can use the difference between ability score and result (eg. ability was 3, result was 1) to indicate degree of success for story telling. (winning by 2 better than winning by 1).

One worry I would have about picking numbers and just subtracting without module to get low numbers is that you get into a kind of odd game-theory situation where obviously the player wants to pick a number in the middle to avoid risk of very low results.

Picking numbers trying to get a high result instead is slightly better because then the player at least has to alternate picking a very high or low number. But then the gm pretty much decides the outcome by choosing something in the middle or not.

And then both try to think about this and try to randomly pick numbers as fair as possible, but I think it would be difficult for the player (or gm) to get out of their head anyway that all numbers are not equal.

Would be interesting to hear if OP tries this how it works out after a while.