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Image of a chess board with some blue and some white tokens.

How many tokens were infected?

Written by Mike McRae

Stuck inside with nothing to do? Grab a chess board and see if you can control an outbreak in this isolation game!


  • A chess board. If you don’t have one, we have a chessboard you can print
  • 12 tokens (coins, plastic discs or draughts)
  • 12 coloured stickers (optional)

The setup

  1. A hand placing a blue token.Place a sticker on the back of every token or coin. Alternatively, if you’re using coins, you can also use tails to identify which tokens are ‘infected’.
  2. Place a single token on each of the four dark squares along the row nearest to you on the chess board. Make sure each token has the sticker facing down, or its head-side facing up.
  3. One blue token between two white tokens on a chess board.Turn one of those tokens over to mark it as ‘infected’.
  4. Place another four tokens on the dark squares of the third row on the chess board.
  5. Blue and white tokens on a chess board.Place the last four tokens on the dark squares on the fifth row on the chess board.
  6. Tokens on a chess board, one has a cross through it.Before we start, keep in mind that all the tokens stay on dark squares – they’re never on the light ones.
  7. Token on a chess board with two diagonal arrows showing possible moves.Tokens always move one space diagonally forwards, either to the left or to the right, and only into empty squares. That means most pieces have two places they can move to, unless they’re on the edge of the board, or there’s a token in the way.

The game

  1. Tokens on a chess board with diagonal arrows showing moves.Move any two uninfected tokens diagonally forward one space.
  2. Tokens on a chess board with diagonal arrows showing moves.Move one infected token diagonally forward one space.
  3. Blue tokens on a chess board.Turn over any uninfected tokens that are adjacent (on one of the surrounding four dark squares) to any infected token. Be careful! If there’s a big group of counters, the infection can spread to all of them!
  4. Repeat steps one to three. Any uninfected tokens that are in the furthest row can be removed from the board during their movement.
  5. Blue and white tokens on a chess board.The round ends when only infected tokens make up the end row or no uninfected tokens remain on the board.
  6. Note down how many tokens were infected.
  7. Repeat the game to see if you can reduce this number.

What’s happening?

It might take a few tries to work out a strategy, but you’ll soon find one way to protect your uninfected tokens is to ensure there is plenty of space around those that are infected. One infected token can infect as many as three others in one move. Those can then in turn each infect up to another three, which can quickly add up.

Many pathogens, such as the virus that causes COVID-19, spread quite easily through infected droplets in the air we cough and sneeze from our lungs. A good, strong cough by a large adult can reach up to 2 metres away, which is why authorities recommend we keep a distance of at least 1.5 metres from most people.

Better still, we should keep away from as many people as possible during outbreaks. Unlike the tokens in this game, many people don’t have an easy way to tell if they’re infected. Called ‘carriers’, they can still produce infected droplets, but don’t show any symptoms.

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  1. cool

  2. it looks fun

  3. Sounds like a fun game.
    Thank you

  4. Reminds me of the ancient computer (like CP/M ancient) game ‘Life’. This added rules about death if too few or too many neighbours and could even result in stable ‘cell patterns’ that would move across the game board.

    1. Life is a very interesting pattern generator!

      It was very sad to hear that John Conway, the inventor of Life, passed away recently due to COVID-19.

  5. Wow! Oh dear. Hope he shuffled off peacefully riding a Schick-Ship Puffer Train.

  6. I wonder if Step 3 is incorrectly illustrated. The far right token in not in the adjacent four dark squares, and therefore should not be infected?

  7. Hi Francis,
    The far right token is adjacent to an infected token – but yes, earlier in the step the infection spread to that token too.

    You can play the game either way – with the infection spreading instantly through a whole group of connected people, or that it only infects one step at a time. Maybe you could even try both, and see which one is easier?

  8. Thanks David.

    Starting with the board position illustrated (with the uninfected token shown and 11 uninfected tokens), the best I could do was leaving seven uninfected tokens. I had to move the infected token left to make this happen (to hasten infected tokens to move to the top left corner and fill up the top row). Is this the best possible?

    Of course, the absolute maximum is eight uninfected tokens (as four of the 12 must be infected). I could not make this happen.

    Yes, someone did look into this game?!



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