https://codepen.io/osublake/pen/oLGBXy
I've just studied this demo. And I found something weired to me.
When you look very carefully at those particles, you will find they have short trails after them.
In the 9th line of the code. If you change the variable 'fade' from 'rgba(0,0,0,0.4) to 'rgb(0,0,0). The particles' trails will all disapear.
What is confusing me is that I don't understand why the particles can have those short trails. Becuase we didn't draw the trails manually on the canvas. I have an assumption is it's due to persistence of vision. But it doesn't make sense, trails disapeared when 'fade' was equal to 'rgb(0,0,0)'.
Does anybody know why?