SpriteKit

GameplayKit is a collection of foundational tools and technologies for building games in iOS, OS X, and tvOS. Building, evolving, and maintaining a sophisticated game requires a well-planned design, GameplayKit provides architectural tools to help you design modular, scalable game architecture with minimal effort. Creating great games also requires deploying complex algorithms to solve the problems underlying common game mechanics, GameplayKit also provides standard implementations of such algorithms, allowing you to spend more time on the features that make your gameplay unique. Because GameplayKit is independent of high-level game engine technologies, you can combine it with any of those technologies to build a complete game, SpriteKit for 2D games, SceneKit for 3D games, or a custom or third-party game engine using Metal or OpenGL ES. For games with less demanding graphics needs, you can even use GameplayKit with UIKit (in iOS or tvOS) or AppKit (in OS X).

Aseprite lets you create 2D animations for video games. From sprites, to pixel-art, retro style graphics, and whatever you like about the 8-bit and 16-bit era. It has a color mode, which tell you how many colors the image can handle. All images in the sprite are in one specific mode, you cannot mix RGB images with Indexed images in the same sprite. It contains a set of layers. You can see them in the Timeline. The most important concept here is that there are two kind of layers: the background layer for opaque sprites, and transparent layers. A sprite can contain only one background layer, but several transparent layers. It contains animation frames. Each frame has a duration, i.e. how many milliseconds the frame must be on screen when the animation is being played. Integrate Aseprite in your assets pipeline with the command-line interface (CLI). Store several animations in one texture atlas.