Ever seen a stereo or a sound system with bars that reflect the beat of the music. This circuit does much the same thing.This is done through a loop that observes changes in loudness and lights a number of LED's that corresponds to that change.
In the video you will see how the code works and see it respond to voice and music.
•4 x LED (5mm)
•4 x Resistor 300Ω
p.s: too easy for ya?, well its a part of a free, fully documented (programs+schematics) online course designed to get young kids into electronics, so if you think it's any good pass it on?
Handouts + Schematics available on robotix.com.au/tutorials for free download