$selected_cat = isset($_GET['cat']) ? sanitize_text_field($_GET['cat']) : '';

$args = array(
    'post_type'      => 'product',
    'posts_per_page' => 12,
);

// If a category is selected, filter products by that category
if (!empty($selected_cat)) {
    $args['tax_query'] = array(
        array(
            'taxonomy' => 'product_cat',
            'field'    => 'slug',
            'terms'    => $selected_cat,
        ),
    );
}

$loop = new WP_Query($args);

if ($loop->have_posts()) :
    echo '<div class="projects-grid">';
    while ($loop->have_posts()) : $loop->the_post(); global $product;
        // Your product card here
    endwhile;
    echo '</div>';
else :
    echo '<p>No products found in this category.</p>';
endif;

wp_reset_postdata();