The first thing we add is the sound effects, to give feedback to the user when something, either good or bad, happens in the game. For example, we could notify that the bird is flapping, or has hit the pipes, using a sound.

There are basically two ways for an indie game developer—which means a developer without any video game publisher's financial support—to add sounds to the game: creating them, or searching for them from sound collections such as https://www.freesound.org or http://www.freesfx.co.uk.

Because the aim of this book is to teach you how to create apps using Swift, we'll use some resources found in a free collection.

In the master branch, you can find .zip files with all the required sounds.