These example themes demonstrate 3 varied but idiomatic approaches to styling the dropdown menu.
For maximum consumability, they are written in vanilla CSS, and as such do not include any niceties such as variables or vendor prefixes.
If you plan to use or adapt any of these themes for your project, it is your responsibility to ensure the appropriate vendor prefixes (e.g for CSS transforms) are applied for your desired browser support.
We recommend post-CSS for this purpose.