Collision.js

this.collidesWith = function(otherObject) {
  var width = 2*this.radius;
  var height = 2*this.radius;
  var translatedX = this.x - radius;
  var translatedY = this.y - radius;
  
  if (translatedX < otherObject.x + otherObject.width &&
     translatedX + width > otherObject.x &&
     translatedY < otherObject.y + otherObject.height &&
     height + translatedY > otherObject.y) {
      // collision detected!
  }
}