sketch.js

var fixedrect, movingrect;

function setup() {
  createCanvas(800,400);
  fixedrect = createSprite(400, 200, 150, 50);
  fixedrect.shapeColor = "hotpink";

  movingrect = createSprite(200,100, 80,40);
  movingrect.shapeColor = "cyan";
}

function draw() {
  background(0);  

  movingrect.x = World.mouseX;
  movingrect.y = World.mouseY;

  if(movingrect.x - fixedrect.x < movingrect.width/2 + fixedrect.width/2 && 
    fixedrect.x - movingrect.x < movingrect.width/2 + fixedrect.width/2 &&
    movingrect.y - fixedrect.y < movingrect.height/2 + fixedrect.height/2 &&
    fixedrect.y - movingrect.y < movingrect.height/2 + fixedrect.height/2){
      
    movingrect.shapeColor = "red";
    fixedrect.shapeColor = "red";
  }
  else{
    fixedrect.shapeColor = "hotpink";
    movingrect.shapeColor = "cyan";
  }

  drawSprites();
}