What is the 'superpowers' tool for Claude Code, and where do I get it?

Superpowers is described as an open-source tool for use with Claude Code (or similar coding-agent tools) that functions like 'planning mode on steroids.' It runs the planning process and then writes up a detailed spec -- described as ending up with roughly a 5,000-line markdown document -- before any code is actually built. The member using it said this prevents the resulting app from being 'really bad ... that breaks all the time,' and that even as a non-developer, superpowers both helps flesh out what you want to build during planning and produces code that actually works. It was noted to be one of a few similar planning tools available, described as probably the most popular one, though the exact source/repo location wasn't specified beyond it being open-source.