Let it snow: falling snow on every figure!

This submission was inspired by the google 'let it snow' effect (for those who

don't already know this, try searching 'let it snow' with google and see what

will happen). However, this implementation does not include the frosty window effect as

seen in the google version, since I really can't make the rendering fast

enough for MATLAB.

How to use:
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Type 'letitsnow' and snow will fall on your CURRENT figure. If no figure

exists, an empty one will be created.

You can also use 'letitsnow(figure_hdl, color)' to specify in which figure the

snow should appear and what color the snow is.

Use 'help letitsnow' for more information

How to stop the snow:
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Press 's' key on the figure or close the figure.

Note:
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The falling snow animation runs in a 'non-blocking' way. That is, you can run

other scripts while the snow is falling.

It is also possible to make multiple figures snow at the same time.

This function works regardless of the content of the figure. So you can draw

a christmas tree and then run letitsnow for more christmas festivity. For a

good christmas tree plot, look at submission #22478 by Anselm.

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Happy Holidays!