build a theme in wordpress code example

Example 1: function for style your theme wordpress

function register_styles() {
  wp_register_style( 'theme_styles', get_template_directory_uri() . '/styles/main_global.css' );
  wp_enqueue_style( 'theme_styles' );
}

Example 2: wordpress theme development

You can use this as start theme or as boilerplate for theme
this has all the start up files 

https://github.com/d4rkvent/understrap