let barlimit;

let barx, bary;

function setup() {

  createCanvas(400, 800);

  barx = 200;

  bary = 100;

}

​

function draw() {

  background(250);

  //bar

  fill(210);

  rect(196, 70, 8, 600);

  //slider

  noStroke();

  fill(50, 168, 64);

  slidex = barx;

  slidey = bary;

  circle(slidex, slidey, 60);

}

//mouse movement

function mouseDragged() {

  if (

    mouseX >= slidex - 30 &&

    mouseX <= slidex + 30 &&

    mouseY >= bary - 30 &&

    mouseY <= bary + 30 // make sure it only work inside of the button

  ) {

    bary = constrain(mouseY, 70, 670); // Constrain the movement within the bar

  }

}

​