Play the classic hand game against the computer. Pick Rock, Paper, or Scissors and see who wins each round, with your wins, losses, and draws kept on a running scoreboard.
How it works
When you click a move, the computer independently chooses one of Rock, Paper, or Scissors using the browser’s cryptographically secure random generator with no bias — each option has an equal one-third chance, and there is no memory of past rounds. It then applies the rules to decide the winner:
- Rock beats Scissors
- Scissors beats Paper
- Paper beats Rock
- Matching moves are a draw
The result is shown instantly and the scoreboard updates, which you can reset at any time.
Example
You play Paper and the computer plays Rock. Paper beats Rock, so you win the round and your win count goes up. Next round you play Scissors and the computer plays Rock — Rock beats Scissors, so the computer wins.
| Your move | Computer | Result |
|---|---|---|
| Rock | Scissors | You win |
| Paper | Paper | Draw |
| Scissors | Rock | You lose |
The whole game runs in your browser — nothing is uploaded.
The mathematics of a fair opponent
Against a truly random computer, the expected long-run win rate for any single strategy is exactly one-third — the same as the draw rate and the loss rate. No move is better than another when the opponent chooses uniformly at random. This is unlike human opponents, where most people gravitate toward patterns: novices throw Rock more often (it feels “strong”), and experienced players try to read the patterns of whoever they’re playing.
The cryptographically secure random source used here means the computer has no exploitable pattern — it is as close to a fair coin flip as a browser can produce.
Why the three-move system is elegantly balanced
Rock Paper Scissors works because the three outcomes form a non-transitive cycle: Rock beats Scissors, Scissors beats Paper, and Paper beats Rock. No single option dominates. The game generalises into variants like Rock Paper Scissors Lizard Spock (five moves), where each move beats two others and loses to two others, preserving the cycle but reducing luck by adding complexity.
When to use this
- A quick, fair way to make a two-person decision when neither person can agree
- Testing your own pattern-avoidance (can you really randomise your moves against a fair machine?)
- Showing probability concepts to children — over many rounds, wins converge on roughly one-third each regardless of strategy