ClickBeamLens

let x=0,
    y=0,
    a=100;
function setup() {
  createCanvas(400, 400);
  background(0);
  stroke(255);
  plotP();
}
function draw() {
  translate(width/3,width/2); stroke(random(50,255),random(50,255),random(50,255))
}

function mousePressed(){
  if(mouseX-width/2>width/3-a){
    msX = mouseX- width/3;
    msY = mouseY-width/2;
    m = (msY)/(msX-a);
    a1 = m*m;
    b1 = -(2*a*m*m+4*a);
    c1 = a*a*m*m;
    tmp = (b1*b1-4*a1*c1)
    x1 = (-b1-sqrt(tmp))/(2*a1);
    y1 = sqrt(4*a*x1);
    if(msY<0){
      line(msX,msY,x1,y1);
      line(x1,y1,width,y1)
    }
    if(msY>=0){
      line(msX,msY,x1,-y1);
      line(x1,-y1,width,-y1)
    }
  }
}

function plotP(){
  translate(width/3,width/2);
  for (i=-100;i<100;i=i+1){
    t=i/90;
    y=2*a*t;
    x=a*t*t;
    circle(x,y,2);
    circle(a,0,10);
    line(-a,-width/2,-a,width/2)
  }
}