var screenSize: NSSize!

override func didMove(to view: SKView) {
    screen = self.view?.frame.size

    addCanvasNode()
}

fileprivate func addCanvasNode() {
    canvasNode = SKShapeNode(rect: CGRect(x: -screen.width / 2, y: -screen.height / 2, width: screen.width, height: screen.height))
    canvasNode.fillColor = .brown
    addChild(canvasNode)
}