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Strategy

The 21 Coins Game

Strategic Thinking & Decision-Making

Preview

The Scenario

Twenty-one gold coins sit on the table. You and the computer take turns, and you go first. On each turn you take 1, 2, or 3 coins into your chest — whoever grabs the very last coin wins. It looks like luck, but there is a hidden pattern. Outsmart the machine by thinking a few moves ahead, and discover the winning strategy hiding in plain sight.

How to Play

How to Play

  1. There are 21 gold coins on the table.
  2. You and the computer take turns — you go first.
  3. On each turn, drag 1, 2, or 3 coins into your chest.
  4. Whoever takes the very last coin wins!

What You'll Gain

  • Experience how thinking ahead beats reacting in the moment
  • Discover backward reasoning — solving a problem by starting from the end goal
  • Learn to spot patterns and rules in situations that first look random
  • Build confidence making deliberate decisions rather than guessing
  • A quick, playful warm-up that gets people into a problem-solving mindset

Main Features

  • 21 gold coins shared between you and the computer
  • Turn-based play — you always go first
  • Take 1, 2, or 3 coins per turn into your chest
  • Last coin taken wins the round
  • A computer opponent that plays the optimal strategy
  • Quick replay to test and refine your approach

Knowledge Terms Covered

  • Game theory
  • Backward induction
  • Winning strategy
  • Turn-based play
  • Optimal move
  • The game of Nim
  • Losing positions