Tina4 CSS is a Tina4 module that provides a base CSS, which can be used as is, or can be added to for the CSS for your project.
Tina4 CSS files are found in the path
\vendor\andrevanzuydam\tina4-css\src\scss\
Any files used to overwrite the Tina4 CSS should be in the project folder path
\src\scss\
The module is naturally included through the composer file autoloader.
The generated CSS file default.css will be in the projet folder path
\src\assets\css\
Tina4 CSS will automatically regenerate the CSS file, on the first load of Tina4, if the generated file default.css is deleted.
Should you decide to modify the generated CSS files, it is recommended that you change the file names, to avoid them getting overwritten, should the compile function be invoked.