It seems that LEDs not only produce light but can be made to detect light (I guess it's similar to turning an electric motor to generate voltage). Here's a video of a cool LED/computer interface controlling a matrix of 3d cubes:
click for video
I have a big box of LEDs, I just wish I had the smarts to replicate this

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Very cool. I do electronics for a living right now, so I have the abilities and parts around me... just not the knowledge
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Your post was actually old news