function particle(x, y) {
        this.x = this.px = x;
        this.y = this.py = y;
        this.xv = this.yv = 0;
    }
//This function is used to create a particle object.
This function is used to create a particle object.
This function is used to create a particle object .
function particle(x, y) {
        this.x = this.px = x;
        this.y = this.py = y;
        this.xv = this.yv = 0;
    }
function particle ( x , y ) { this . x = this . px = x ; this . y = this . py = y ; this . xv = this . yv = 0 ; }
This function is used to create a particle object.
This function is used to create a particle object .