Hello,
It’s a simple beat detector.
Searches for beats in the sample and places a marker in its place.
The main word in it has a lowpass filter so it won’t find beats in higher frequencies (hi-hat and others).
It is prone to noise so the cleaner the sample the better 
It’s just another option for zero crossing, but it’s more about something else.
With long samples, of course, detection ends at the 255 marker.
It’s just a toy, use at your own risk.