Using Non-standard CSS

[lounsbrough]

https://github.com/lounsbrough/codenough.com/blob/6b444c67b144700bc3a4975e53d3f5799de300c1/src/css/_proficiencies.scss#L53

The -webkit-tap-highlight-color feature is non standard, and a better solution should be found to avoid the mobile flickering/highlighting on click.

https://developer.mozilla.org/en-US/docs/Web/CSS/-webkit-tap-highlight-color