purecss.io usage for WordPress themes

Activating the plugin doesn't do anything by itself. You'll want to use add_theme_support().

Somewhere in your "after_setup_theme" action handler, do this

add_theme_support( "pure-css" );

This loads the latest version of Pure CSS base library using "wp_enqueue_scripts" action.

Load more Pure modules

add_theme_support( "pure-css", array( "grids", "forms" ) );

add_filter( "pure_css_version", function( $version ) { return "0.4.2"; } );