wp_twentytwentyone-child-spring2life/template-parts/header/titlepage-header.php

<?php
/**
 * Displays the site header.
 *
 * @package WordPress
 * @subpackage Twenty_Twenty_One
 * @since Twenty Twenty-One 1.0
 */

$wrapper_classes  = 'site-header';
$wrapper_classes .= has_custom_logo() ? ' has-logo' : '';
$wrapper_classes .= true === get_theme_mod( 'display_title_and_tagline', true ) ? ' has-title-and-tagline' : '';
$wrapper_classes .= has_nav_menu( 'primary' ) ? ' has-menu' : '';
?>

<!-- https://www.cssscript.com/morphing-side-menu-with-pure-css-css3/ -->
<input type="checkbox" id="menuTrigger"/>
<div class="menu">
  <label for="menuTrigger" class="trigger">
    <div class="line"></div>
    <div class="line"></div>
    <div class="line"></div>
  </label>
</div>
<header id="masthead" class="<?php echo esc_attr( $wrapper_classes ); ?>" role="banner">

	<?php get_template_part( 'template-parts/header/site-branding' ); ?>
	<?php get_template_part( 'template-parts/header/site-nav' ); ?>

</header><!-- #masthead -->