 extension Bird {
     func flap() {
         node.physicsBody!.velocity = CGVector(dx: 0, dy: 0)
-        node.physicsBody!.applyImpulse(CGVector(dx: 0, dy: 8))
+        node.physicsBody!.applyImpulse(CGVector(dx: 0, dy: 6))
     }
     
     func update() {

    }
}



    func createNode() -> SKSpriteNode {
        let birdNode = SKSpriteNode(imageNamed: textureNames.first!)
        birdNode.zPosition = 2.0
        birdNode.physicsBody = SKPhysicsBody.rectSize(birdNode.size.scale(0.8)) {
            body in
            body.dynamic = true
            body.categoryBitMask    = BodyType.bird.rawValue
