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Wild Tic-tac-toe

Read this article where Yossi Elran explains about wild tic-tac-toe
Wild tic-tac-toe
© Davidson Institute of Science Education, Weizmann Institute of Science
Wild tic-tac-toe is my favourite variation on tic-tac-toe.
Instead of one player always drawing ‘X’ and the other ‘O’, each player can draw whatever he chooses on his turn – ‘X’ or ‘O’! This might sound preposterous! How do we know who the winner is? The answer is, of course, that the player who completes a three-in-a-row is the winner, regardless of what the symbol is. Wild tic-tac-toe is not very interesting. If played carefully the first player is a decisive winner. He does this by playing the center square. For convenience, the first player is blue and the second, red.
If the second (red) player responds with a corner ‘X’, he immediately creates a winning situation for the first (blue) player who completes the diagonal with his ‘X’.
Wild tic-tac-toe board 1
If the second (red) player responds with a middle side ‘X’, he does no better.
Wild tic-tac-toe board 2
If the second (red) player responds with a corner ‘O’, the first (blue) player plays the other diagonal with an ‘O’. Whatever the second (red) player does now, whether ‘X’ or ‘O’, he will lose.
Wild tic-tac-toe board 3
By responding with an ‘O’ in a middle side square, the second (red) player can delay his loss.
Wild tic-tac-toe board 4
But only for one more turn…
Wild tic-tac-toe board 5
Thane Plambeck, a good friend of mine, shows some more tic-tac-toe variations in an interview to the excellent Numberphile channel in the following You Tube videos:

This is an additional video, hosted on YouTube.

This is an additional video, hosted on YouTube.

Discussion

Do you know any other tic-tac-toe variations?
© Davidson Institute of Science Education, Weizmann Institute of Science
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