itch.io

Focused on imparting a skill, lesson, or piece of information to its player that would be helpful to them in other aspects of life, such as a faster typing ability or knowledge about a period in history.

Things that are available on GitHub

Pretty sure everything is indie on itch.io but just in case you want something extra indie.

Contains (or is themed around interacting with) a musical score, soundtrack, or backing track(s).

Games that can be played alone