Un-comment out additional boxes in "index.html" to mess around with more examples
Un-comment out lines in "style.css" to align items vertically or horizontally.
Additionally you can open the window in a new tab (top right of the preview window).
Here you can open the developer tools with Ctrl + Shift + I or Command +
Shift + I.
Make sure to inspect the div with the class container and you will see all the css rules. There you can simply check and uncheck whatever properties you want to test out.
Developer window