diff --git a/inc/bootstrap-wp-gallery.php b/inc/bootstrap-wp-gallery.php
index a2f56f6..6ccc70c 100644
--- a/inc/bootstrap-wp-gallery.php
+++ b/inc/bootstrap-wp-gallery.php
@@ -1,129 +1,105 @@
 <?php
-//Based on Jeff Hays code and his article here: http://robido.com/wordpress/wordpress-gallery-filter-to-modify-the-html-output-of-the-default-gallery-shortcode-and-style/ 
-// Custom filter function to modify default gallery shortcode output
-function bootstrap_wp_gallery( $output, $attr ) {
+//Based on Roots Sage Gallery: https://github.com/roots/sage/blob/5b9786b8ceecfe717db55666efe5bcf0c9e1801c/lib/gallery.php
 
+// Remove built in shortcode
+remove_shortcode('gallery', 'gallery_shortcode');
 
-	// Initialize
-	global $post, $wp_locale;
-
-	// Gallery instance counter
-	static $instance = 0;
-	$instance++;
-
-	// Validate the author's orderby attribute
-	if ( isset( $attr['orderby'] ) ) {
-		$attr['orderby'] = sanitize_sql_orderby( $attr['orderby'] );
-		if ( ! $attr['orderby'] ) unset( $attr['orderby'] );
-	}
-
-	// Get attributes from shortcode
-	extract( shortcode_atts( array(
-		'order'      => 'ASC',
-		'orderby'    => 'menu_order ID',
-		'id'         => $post->ID,
-		'itemtag'    => 'div',
-		'icontag'    => 'div',
-		'captiontag' => 'div',
-		'columns'    => 3,
-		'size'       => 'thumbnail',
-		'exclude'    => ''
-	), $attr ) );
-
-	// Initialize
-	$id = intval( $id );
-	$attachments = array();
-	if ( $order == 'RAND' ) $orderby = 'none';
-
-
-	if ( ! empty( $include ) ) {
-
-		// Include attribute is present
-		$include = preg_replace( '/[^0-9,]+/', '', $include );
-		$_attachments = get_posts( array( 'include' => $include, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby ) );
-
-		// Setup attachments array
-		foreach ( $_attachments as $key => $val ) {
-			$attachments[ $val->ID ] = $_attachments[ $key ];
-		}
-
-	} else if ( ! empty( $exclude ) ) {
-
-		// Exclude attribute is present 
-		$exclude = preg_replace( '/[^0-9,]+/', '', $exclude );
-
-		// Setup attachments array
-		$attachments = get_children( array( 'post_parent' => $id, 'exclude' => $exclude, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby ) );
-	} else {
-		// Setup attachments array
-		$attachments = get_children( array( 'post_parent' => $id, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby ) );
-	}
-
-	if ( empty( $attachments ) ) return '';
-
-	// Filter gallery differently for feeds
-	if ( is_feed() ) {
-		$output = "\n";
-		foreach ( $attachments as $att_id => $attachment ) $output .= wp_get_attachment_link( $att_id, $size, true ) . "\n";
-		return $output;
-	}
-
-	// Filter tags and attributes
-	$itemtag = tag_escape( $itemtag );
-	$captiontag = tag_escape( $captiontag );
-	$columns = intval( $columns );
-	$itemwidth = $columns > 0 ? floor( 12 / $columns ) : 100;
-	$float = is_rtl() ? 'right' : 'left';
-	$selector = "gallery-{$instance}";
-
- // Filter gallery CSS
-	$output = apply_filters( 'gallery_style', "
-
-		<div id='$selector' class='gallery galleryid-{$id} row'>"
-	);
-
-	// Iterate through the attachments in this gallery instance
-	$i = 0;
-	foreach ( $attachments as $id => $attachment ) {
-
-		// Attachment link
-		$link = isset( $attr['link'] ) && 'file' == $attr['link'] ? wp_get_attachment_link( $id, $size, false, false ) : wp_get_attachment_link( $id, $size, true, false ); 
-
-		// Start itemtag
-		$output .= "<{$itemtag} class='gallery-item col-md-{$itemwidth}'>";
-
-		// icontag
-		$output .= "
-		<{$icontag} class='gallery-icon'>
-			$link
-		</{$icontag}>";
-
-		if ( $captiontag && trim( $attachment->post_excerpt ) ) {
-
-			// captiontag
-			$output .= "
-			<{$captiontag} class='gallery-caption'>
-				" . wptexturize($attachment->post_excerpt) . "
-			</{$captiontag}>";
-
-		}
-
-		// End itemtag
-		$output .= "</{$itemtag}>";
-
-		// Line breaks by columns set
-		if($columns > 0 && ++$i % $columns == 0) $output .= '<br style="clear: both">';
-
-	}
-
-	// End gallery output
-	$output .= "
-		<br style='clear: both;'>
-	</div>\n";
-
-	return $output;
-
+// Replace with custom shortcode
+function shortcode_gallery($attr) {
+  $post = get_post();
+  static $instance = 0;
+  $instance++;
+  if (!empty($attr['ids'])) {
+    if (empty($attr['orderby'])) {
+      $attr['orderby'] = 'post__in';
+    }
+    $attr['include'] = $attr['ids'];
+  }
+  $output = apply_filters('post_gallery', '', $attr);
+  if ($output != '') {
+    return $output;
+  }
+  if (isset($attr['orderby'])) {
+    $attr['orderby'] = sanitize_sql_orderby($attr['orderby']);
+    if (!$attr['orderby']) {
+      unset($attr['orderby']);
+    }
+  }
+  extract(shortcode_atts([
+    'order'      => 'ASC',
+    'orderby'    => 'menu_order ID',
+    'id'         => $post->ID,
+    'itemtag'    => '',
+    'icontag'    => '',
+    'captiontag' => '',
+    'columns'    => 3,
+    'size'       => 'thumbnail',
+    'include'    => '',
+    'exclude'    => '',
+    'link'       => ''
+  ], $attr));
+  $id = intval($id);
+  $columns = (12 % $columns == 0) ? $columns : 3;
+  $grid = sprintf('col-sm-%1$s col-lg-%1$s', 12 / $columns);
+  if ($order === 'RAND') {
+    $orderby = 'none';
+  }
+  if (!empty($include)) {
+    $_attachments = get_posts(['include' => $include, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby]);
+    $attachments = [];
+    foreach ($_attachments as $key => $val) {
+      $attachments[$val->ID] = $_attachments[$key];
+    }
+  } elseif (!empty($exclude)) {
+    $attachments = get_children(['post_parent' => $id, 'exclude' => $exclude, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby]);
+  } else {
+    $attachments = get_children(['post_parent' => $id, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby]);
+  }
+  if (empty($attachments)) {
+    return '';
+  }
+  if (is_feed()) {
+    $output = "\n";
+    foreach ($attachments as $att_id => $attachment) {
+      $output .= wp_get_attachment_link($att_id, $size, true) . "\n";
+    }
+    return $output;
+  }
+  $unique = (get_query_var('page')) ? $instance . '-p' . get_query_var('page') : $instance;
+  $output = '<div class="gallery gallery-' . $id . '-' . $unique . '">';
+  $i = 0;
+  foreach ($attachments as $id => $attachment) {
+    switch($link) {
+      case 'file':
+        $image = wp_get_attachment_link($id, $size, false, false);
+        break;
+      case 'none':
+        $image = wp_get_attachment_image($id, $size, false, ['class' => 'thumbnail img-thumbnail']);
+        break;
+      default:
+        $image = wp_get_attachment_link($id, $size, true, false);
+        break;
+    }
+    $output .= ($i % $columns == 0) ? '<div class="row gallery-row">' : '';
+    $output .= '<div class="' . $grid .'">' . $image;
+    if (trim($attachment->post_excerpt)) {
+      $output .= '<div class="caption hidden">' . wptexturize($attachment->post_excerpt) . '</div>';
+    }
+    $output .= '</div>';
+    $i++;
+    $output .= ($i % $columns == 0) ? '</div>' : '';
+  }
+  $output .= ($i % $columns != 0 ) ? '</div>' : '';
+  $output .= '</div>';
+  return $output;
 }
+add_shortcode('gallery', 'shortcode_gallery');
 
-// Apply filter to default gallery shortcode
-add_filter( 'post_gallery', 'bootstrap_wp_gallery', 10, 2 );
+/**
+ * Add class="thumbnail img-thumbnail" to attachment items
+ */
+function attachment_link_class($html) {
+  $html = str_replace('<a', '<a class="thumbnail img-thumbnail"', $html);
+  return $html;
+}
+add_filter('wp_get_attachment_link', 'attachment_link_class', 10, 1);