Friction in SpriteKit
问题 I'm working with Swift, SpriteKit and Xcode 6, I have a circle node on my screen and I can change the node's position with my finger, but I would like to implement a friction effect to this node, but I don't now how to do so, here's my code : class PlayScene: SKScene { let firstCircle = SKSpriteNode(imageNamed: "Circle") // theses 3 variables allows me to move the node according to my finger, but my finger don't have to touch the node var departCircleLocation = CGPoint() var