SCSS(SASS) FLEX GRID Core Theory (PDF) and Usage Examples is a PDF textbook that summarizes the core theory of using SCSS(SASS), FLEX, and GRID in an easy-to-understand manner. For those aiming for intermediate to advanced publishing skills, understanding and using SCSS(SASS), FLEX, and GRID is essential. And I think it will be a great competitive advantage for publishing employment and job changes. In addition to the SCSS(SASS) FLEX GRID Core Theory (PDF), the completed theory usage examples (html, scss, css) are attached separately so that you can create applied examples using the theory after learning the theory.