   this.ppy = 1 - this.rad;
        }

        this.t += 1;
        if(this.t % 100 === 0) {
          this.tx = Math.random(); // reset the target location
          this.ty = Math.random();
        }

        // if(this.t % 73 === 0) {
        //   this.tx2 = Math.random(); // reset the target location
        //   this.ty2 = Math.random();
        // }

        // compute distances
        var dx = this.ppx - this.tx;
        var dy = this.ppy - this.ty;
        var d1 = Math.sqrt(dx*dx+dy*dy);

        