How to play with the applet of "goishi" (GO game marbles) example of proof animation.

[add] button adds a black marble in the bag.

Clicking a black marble turns it to a white marble.

[start] button starts the game.

[left] button selects the group A, the green group.

[right] button selects the group B, the yellow group.

An example of the game

- Add four marbles B W B B to the bag. B is a black marble and W is a white marble.
- This bag contradicts to the theorem. Thus something will be wrong with at least one of the two induction hypotheses.
- Actually, both are wrong for this case. Let's select right this time.
- For W B B, the induction hypothesis on group A (green) is wrong and the induction hypothesis on group B (yellow) is correct. A bug will be on group A hypothesis. Thus select left.
- Then you will see what's wrong!
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