Spectre.css is a lightweight, responsive and modern CSS framework.

• Lightweight (~10KB gzipped) starting point for your projects
• Flexbox-based, responsive and mobile-friendly layout
• Elegantly designed and developed elements and components

Spectre is a side project based on years of CSS development work on a large web service project. Spectre only includes modern base styles, responsive layout system, pure CSS components and utilities, and it can be modified for your project with Sass/Scss compiler.

Link: GitHub | Docs & Demo