A new version of the Apple SDK is available on the Downloads page. The latest Xcode 8.3.x release broke the project generation for Swift based projects. The new version of the Apple SDK fixes this. There are no other changes, so the non-Apple platform SDKs are not affected and you will not need to download new versions of those.
Also, the example code from the try! Swift Intro to Game Programming Workshop with SDL is available for download.
It covers: the event loop, event handling, audio (ALmixer), textures (SDL_gpu), and shaders (GLSL).
The idea behind the projects is there is a natural progression of code. There is a baseline project, and each lesson builds a little more from the prior. (They are numbered.) The projects with ‘b’ in the name are the completed solutions to each lesson. I was going to to have an ‘a’ which was supposed to be the starting point, but for various reasons, I don’t always have an ‘a’ and the immediate ‘b’ project preceding it in the category serves as the next project’s ‘a’.
Final lesson (shaders with SDL_gpu and GLSL: ripple effect)