I created this as a tool for playing around with different font and color combinations then generating a theme object that meets the System UI Theme Specification for creating interoperable UI components (see system-ui.com). The idea is that you can quickly experiment, and then if you come up with something you like, you can take those style properties and use them to make your component libraries or with popular projects like Theme UI, Rebass, Primer, Chakra UI, etc.