Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
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Anonymous Chess

Setup a chessboard in your workplace or home. Anyone should be encouraged to come up to the board, weigh the possibilities and make a move for either side. This is an ongoing game that will last for several days. Since anyone can play for either side, there are no winners or losers. In reality, everyone is a winner because this game introduces some novelty [ For more on 'novelty' go here: http://www.braingle.com/mind/351.html ] into the players' day and gives them a chance to exercise a different part of their brains. Often a workday can be filled with drudgery. This is a good way to liven it up a little.
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For more mind exercises: http://www.braingle.com/mind/