Apple announced Swift 2 at WWDC and it's got some great new features: revised error handling, guard statements for better optional binding, protocol extensions, Objective-C generics and lots more. Greg Heo reviews these and other new features in Swift 2.
In Part 1 of this tutorial, you built up impulse resolution. Build on your work and add integration, time stepping and collision detection. You'll also learn how to design your custom physics engine in a modular fashion to make it easier to debug and extend. This is neat stuff. Even if you don't want to create your own physics engine, this article will give you insights into why existing engines are written the way they are.
Just what we've been waiting for: an Entity Component System built right into iOS and OS X. Apple announced GameplayKit at WWDC and it has some really useful features. For example: entity and component classes, randomization utilities, state machine support, minimax, pathfinding, agents and much more. You can use these in all of your iOS games and you'll no longer need to build this code yourself or bring in third party dependencies.