Rock Paper Scissors & Diplomatic RPS

An early RPS match

Scissors cuts paper

Paper covers rock

Rock crushes scissors

I ran Team Rock several DRPS matches

Rock Paper Scissors

Rock paper scissors (or roshambo) has been a staple since high school. Usually 3-5 minutes are spent before each throw psyching an opponent out and trying to get in his head. Those who think it is a game of random chance are sorely mistaken. Whenever people find out I am a card carrying member of the World RPS Society they line up to challenge me hoping in vain to prove the game is random. Usually after a few defeats (inlcuding multiple telegraphed throws) they either admit I dominate or claim I'm very lucky.

Computers are a bit tougher... you can't reason with them or psych them out. Who among us hasn't wasted many a night going head to head with the Roshambot? That thing is brutal. It can bring you right to the brink of total dispair. If you really want to get a glipse into the seedy underworld of computerized roshambo, take a gander at the First International RoShamBo Programming Competition and the Second International Roshambo Programming Competition. I was particularly entertained by the Unofficial Super-Modified Class competition.

Check out the Rock Paper Scissors Strategy Guide to brush up quickly. Or read some advanced strategy online.

Diplomatic RPS

My friend Ryan invented a RPS variant called Diplocatic RPS. The aim was to combine elements of Diplomacy and RPS.

Rules

The rules are quite simple:

1. Any number of people make RPS throws simultaneously (either standing in a circle or by writing them down).
2. If all three throws are represented, the throw with the least "votes" is eliminated.
3. If only two throws are represented, standard RPS rules apply.
4. Repeat until only 1 player is left.

Gameplay

In practice with large numbers of people early rounds become like political conventions. It's a safe bet that all three throws will be represented, so players form alliances to ensure their throw will be the most popular. For example, in our Internet games by email with one throw each day I formed Team Rock and acted as the party whip. In mid rounds a successful team will doublecross a few members setting them up as fall guys to do a losing throw, which will ensure that the rest of the team cannot be eliminated. Eventually when there are few enough players that it is likely not all three throws will be represented, teams dissolve as members start doublecrossing hoping to eliminate the whole team with one throw. It's very entertaining.

Scoring

The scoring is a little complicated. At the beginning of the game, everyone antes 1 rating point. Whenever you are eliminated, you lose that rating point, and the players who survived the round get to divide up your rating point for themselves. They do not, however, get a share of the rating points that you may have earned from the elimination of other players in previous rounds. All players who are eliminated in the same round of a game will have their ratings changed by the same value. Ratings are cumulative from game to game.

Example games