Smart phone app that throws Rock/Paper/Scissors

[Doctor Awkward]

The majority of WoD games in my area tend towards LARPs, which use a rock, paper, scissors mechanic to resolve challenges.

I don't like this approach on account of it becoming largely a psychology contest between two players rather than a probability test between two characters abilities.

Both of the organized groups I know of allow for either RPS dice or a smart phone app that would randomly choose for me.

Does anyone know of, or use, a good app for this?

[Totally Guy]

I know someone who wears a watch for things like that. He'll look at the second hand and make (arbitrary) decisions based on which third, quarter or half it occupies.

[JeenLeen]

If there's not, you could use a d6 emulator and use 1-2 for rock, 3-4 for paper, and 5-6 for scissors. Or something similar.

That said, I reckon there is one out there somewhere. If you find it, test it for how reliable it is. It'd be poor form (and possibly look like cheating) if the other person 'throws' while your tech glitches out and you have to ask for a redo (though I would hope folk would be understanding.)

I think this is an awesome idea for improving fairness of the system.

[meschlum]

Game theory time!

When playing RPS, assuming you're not cheating (i.e. waiting to see what the other player picks, and making your choice accordingly), there is no optimal strategy with a single choice. If you always play Rock, you'll lose to someone who learns this and always plays Paper...

So we get Mixed strategies instead, where you don't always pick the same option. Again, in theory, if you follow a rule (Rock, then Paper, repeat, for instance), someone else playing against you can learn the rule and always win (playing Paper then Scissors in the example above). You need to randomize your choice!

So you have three choices, which you select with probability R, P, and S.

R + P + S = 1

What happens if R > P and R > S? The other player could play Paper all the time, and win with probability R, losing with probability S - so winning more often than losing, and you'd be losing more often. Which means you don't want R to be more than S or P.

What happens if P > R and P > S? The other player can play Scissors all the time, and again you lose more often than you win.

The same holds if S > P and S > R, so you want R = P = S.

This gives you R = P = S = 1/3 as the optimal strategy, in that the other player will never be able to develop a strategy that lets them win more often than they lose against your strategy.

How do you implement this? Roll a fair D6 (or D12), and assign R / P / S to the results. If you want to avoid timing issues, get an opaque cup, roll the die inside, and flip it over. The other player can take their time to pick Rock, Paper, or Scissors, and you reveal the result.

Rock: 1-2 on D6 (1-4 on D12)
Paper: 3-4 on D6 (5-8 on D12)
Scissors: 5-6 on D6 (9-12 on D12)

If you want to speed things up even more, roll a D6 (or D12), and assign the outcomes directly, since in optimal play the other player will use the same strategy you do.

You Lose: 1-2 on D6 (1-4 on D12)
You Tie: 3-4 on D6 (5-8 on D12)
You Win: 5-6 on D6 (9-12 on D12)

[The Glyphstone]

You can get Rock-Paper-Scissors as a card game for pretty cheap, like $5. Shuffle your deck, then draw one and that is your throw. Quite a few players in the WoD LARP troupe I used to play with did it that way.