let speed = 5;

let directionX = 1;

let directionY = 1;

let side = 20;

let rectA = 300;

​

function setup() {

  createCanvas(600, 600);

  redPosX = 0;

  redPosY = 60;

}

​

function draw() {

  fill(0);

  rect(0, 0, rectA, height);

  fill(255);

  rect(rectA, 0, width - rectA, height);

​

  let currentColor = get(redPosX + side, redPosY);

​

  fill(255);

  rect(redPosX, redPosY, side);

​

  if (currentColor[0] === 255 || currentColor[0] === 255) {

    directionX = directionX * -1;

    rectA += 10;

  }

  if (redPosX < 0) {

    directionX = directionX * -1;

  }

  if (redPosY > height - side || redPosY < 0) {

    directionY = directionY * -1;

  }

​

  redPosX += speed * directionX;

  redPosY += speed * directionY;

​

  for (let i = 0; i < width; i += side) {

    for (let j = 0; j < height; j += side) {

      noFill();

      rect(i, j, side);

    }

  }

}

​