func didBeginContact(contact: SKPhysicsContact) {
var firstBody: SKPhysicsBody
var secondBody: SKPhysicsBody
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
firstBody = contact.bodyA
secondBody = contact.bodyB
} else {
firstBody = contact.bodyB
secondBody = contact.bodyA
}
if ((firstBody.categoryBitMask & PhysicsCategory.Monster != 0) &&
(secondBody.categoryBitMask & PhysicsCategory.Projectile != 0)) {
projectileDidCollideWithMonster(firstBody.node as! SKSpriteNode, monster: secondBody.node as! SK…