Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
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Circle Drawing Exercise

Get a piece of paper and draw a bunch of non-overlapping circles on it (20 will be a good number). Now set a timer for 2 minutes and start doodling. The goal is to use as many of the circles as you can. For example, you may turn one of the circles into an apple by drawing a stem, or you may turn two adjacent circles into a bicycle by drawing the frame. See if you can use all 20 circles in 2 minutes. It's not as easy as you think! Try to create entirely different pictures every time you try this exercise. If circles get too easy, use triangles or squares.
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For more mind exercises: http://www.braingle.com/mind/