let x, y;

// previous x, y

let px, py;

​

 function setup() {

   createCanvas(windowWidth, windowHeight);

   background(255);

​

   // initialize variables

   x = 0;

   y = height / 2;

   px = x;

   py = y;

 }

​

 function draw() {

   // move x by 1 pixel to the right every frame

   x++; // same as x = x + 1

   y = (noise(frameCount * 0.01) - 0.5) * height / 4 + height / 2;

​

   line(px, py, x, y);

​

   // set previous to current

   px = x;

   py = y;

 }