itch.io

Utilizing content created by algorithms rather than human made content. Often utilizes a "seed," a relatively small string that is used to control the randomization algorithm that generates the entire world.

Focused on using its text, moreso than its visuals or audio, to tell the bulk of its story/plot. (Still can have great audio and visuals, though!)

Twine is a free and open source tool for telling interactive, non-linear stories.