Prototype

Odd Coin Out

One coin is fake. Use the balance scale a limited number of times, then accuse the right coin.

    How to play
    • Click a coin to move it onto the left pan, click again for the right pan, again to take it off.
    • Both pans need the same number of coins before you can weigh. The scale tells you which pan went down, or that they balanced.
    • Weighings are limited. When you're sure, press Accuse a coin and click the fake. In the hardest tier you must also say whether it is heavier or lighter.
    • Turn on the assist to see which coins the evidence has already ruled out — or turn it off and track it in your head.

    What it teaches: information. A weighing is a three-way question, so k weighings can separate at most 3k cases. The tiers are sized right at that limit — the classic 12-coin problem has 24 possibilities against 27 outcomes.