createCanvas(400, 400);

}

​

var b1X = 30;

var b1Y = 75;

var b1width = 50;

var b1height = 100;

var b1Color = "white";

​

var b4X = 300;

var b4Y = 350;

var b4width = 50;

var b4height = 50;

var b4Color = "white";

function draw() {

  background(220);

​

  fill(b1Color);

  rect(b1X, b1Y, b1width, b1height);

  fill("black");

  text("B1", b1X + b1width / 3, b1Y + b1height / 3);

​

  fill(b4Color);

  rect(b4X, b4Y, b4width, b4height);

  fill("black");

  text("B4", b4X + b4width / 3, b4Y + b4height / 3);

  b4X = b4X - 1;

  b4Y = b4Y - 1;

​

  if (b4X <= b1X + b1width && b4X + b4width >= b1X &&

        b4Y <= b1Y + b1height && b4Y + b4height >= b1Y) 

  { 

    //code for collision goes here

    b4Color = "yellow";

  } 

  else {

    //if not true -- else is optional

    b4Color = "white";

  }

}

​