How To Win at Rock-Paper-Scissors

Intro

There are 3 basic rules to the game of Rock Paper Scissors. You and one opponent both hold out a closed fist and count down, usually with a "Rock, Paper, Scissors" or "Rock, Paper, Scissors, Shoot." Clarify with your opponent beforehand to make sure you both are on the same page in terms of the countdown method. During this time, you both will think of Rock, Paper, or Scissors at random (ideally) and use the appropriate hand gesture to display which object you had chosen.

Game Rules

Paper beats Rock
Rock beats Scissors
Scissors beat Paper

A tie can occur if both you and your opponent play the same object.

Although random gameplay is ideal for Rock Paper Scissors, this is almost never the case, unless with computers, but even then, 'random' is arguable. Human behavior randomness can be easily predictable. This creates flaws in the (ideally random) game of Rock Paper Scissors. With this knowledge, there are 3 basic rules to winning the game of Rock Paper Scissors.

Behavioral Rules

Winners stay the same.
Losers change.
Your opponent may know rules 1 and 2, even if subconciously.

So, how do you win at Rock Paper Scissors? It's not that simple. You must consider the knowledge of your opponent to judge which object to play next based on the current play, and this can change throughout the game, usually in this order.

Cases that make the behavioral rules complicated

Your opponent may not know any of these rules above.
Your opponent may know rules 1 and 2.
Your opponent may know rules 1, 2, and 3.

In the following tables, the first horizontal row is your last move and the first vertical column is your opponent's last move. Inside the cells in the table is what your next move should be based on your opponent's predictable behavior.

Case 1

Your opponent does not know the behavioral rules.

They still unknowingly abide by behavioral rules 1 and 2 which makes their next move fairly predictable. For example, if you played Rock and your opponent played Paper, they would win that round. Because they won, they would not likely change their move, sticking to Paper. Knowing their next move, you could play Scissors and win the round. Another example, if they played Scissors and you played Rock, you would win. Knowing they would change to Paper beat your play, you can simply counter with Scissors. A tie is counted as a loss for the opponent, because when you tie, they know their current play cannot win them the game. The following is a table demonstrating all the move possibilities for this case only, showing what move you should play next based on the current play.

v Opp / You >	ROCK	PAPER	SCISSORS
ROCK	scissors	rock	paper
PAPER	scissors	rock	paper
SCISSORS	scissors	rock	paper

Summary: In Case 1, your next move should be whichever object would lose to the one you had just played, regardless of your opponent's move.

Case 2

Your opponent knows behavioral rules 1 and 2.

Your opponent assumes that you will follow rules 1 and 2 and plans their move accordingly. For example, if you played Rock and your opponent played Paper, your opponent would win that round. Assuming that you would change your object to Scissors to beat their Paper, they would play Rock. Therefore, you should play Paper to beat their Rock. Another example, if they played Scissors and you played Rock, you would win that round. Knowing that winners stay the same would cause them to choose Paper to beat your following Rock. However, you can counter by playing Scissors. In the case of a tie, in this example, 2 Rocks are played. Your opponent would assume you would switch to Paper to beat their Rock, so they pick Scissors. You can win the next round by playing Rock again.

v Opp / You >	ROCK	PAPER	SCISSORS
ROCK	rock	rock	rock
PAPER	paper	paper	paper
SCISSORS	scissors	scissors	scissors

Summary: In Case 2, your next move should be what your opponent has just played, regardless of your move.

Case 3

Your opponent knows behavioral rules 1, 2, and 3.

Consider this. Your opponent will follow the same process that you had just went through in Case 2. This table is the same table you saw in Case 2 with the X and Y values switched to show your opponent's moveset instead. Their moves are in the first horizontal row and your moves as the first vertical column.

v You / Opp >	ROCK	PAPER	SCISSORS
ROCK	rock	paper	scissors
PAPER	rock	paper	scissors
SCISSORS	rock	paper	scissors

Therefore, in order to beat your opponent, you must plan your next move to beat your own thought process from Case 2. Just play whichever object will win in each cell of the table shown above. Below is the table for what you should play.

v Opp / You >	ROCK	PAPER	SCISSORS
ROCK	paper	scissors	rock
PAPER	paper	scissors	rock
SCISSORS	paper	scissors	rock

Summary: In Case 3, your next move should be whichever object would beat your current play, regardless of your opponent's move.

There aren't just 3 cases. There are an endless amount which use the same process.

N^th Case Process

Start with the table from the (N-1)^th case.
Flip the X and Y values to see which move your opponent will play.
Play whichever object will beat your opponent's object.

Example: Case 4

Your opponent will follow the same process that you had just went through in Case 3. This table is the same table from Case 3 with the X and Y values switched to show your opponent's moves as the first row and your moves as the first column.

v You / Opp >	ROCK	PAPER	SCISSORS
ROCK	paper	paper	paper
PAPER	scissors	scissors	scissors
SCISSORS	rock	rock	rock

To win, simply pick the object which will beat your opponent's move.

v Opp / You >	ROCK	PAPER	SCISSORS
ROCK	scissors	scissors	scissors
PAPER	rock	rock	rock
SCISSORS	paper	paper	paper

This works for any case, assuming your opponent strictly follows these rules. Of course, there is always some randomness in human behavior, so don't expect this to work all the time. Maybe not even half the time. You will win a truly random game of Rock Paper Scissors only 33.3% of the time. But maybe this guide can give you a few percent boost. Good luck!