sketch.js

var fixedRect, movingRect;
function setup() {
  createCanvas(800,400);
  fixedRect = createSprite(200,200,50,80);
  movingRect = createSprite(400,200,80,30);
  fixedRect.shapeColor = "green";
  movingRect.shapeColor = "green";
}

function draw() {
  background(255,255,255);
  
  movingRect.x = World.mouseX;
  movingRect.y = World.mouseY;
  if(movingRect.x - fixedRect.x <= movingRect.width/2 + fixedRect.width/2
    && movingRect.x - fixedRect.x >= -(fixedRect.width + movingRect.width)/2
    && movingRect.y - fixedRect.y <= movingRect.height/2 + fixedRect.height/2
    && movingRect.y - fixedRect.y >= -(fixedRect.height + movingRect.height)/2) {
    fixedRect.shapeColor = "red";
    movingRect.shapeColor = "red";
  } else {
    fixedRect.shapeColor = "green";
    movingRect.shapeColor = "green";
  }
  drawSprites();
}