From the introduction:
Wretched and Alone (W&A) is a System Reference Document for games based on Chris Bissette’s The Wretched. These systems typically create solo games about struggling alone against insurmountable odds and documenting that struggle.
Generally speaking, they require a block tower, a deck of cards, one or more six-sided dice, and ten tokens of some kind. Some games will vary from this.
This SRD is aimed at designers, writers, and publishers who’d like to publish games that make use of the systems and ideas from The Wretched in their own setting.