diff --git a/app/index.js b/app/index.js
index bbcf63d..1da776e 100644
--- a/app/index.js
+++ b/app/index.js
@@ -313,6 +313,7 @@ function processData(data, filename) {
       currentFileName = filename;
 
       topics = [...new Set(data.flatMap(item => item.topics))].sort();
+      subtopics = [...new Set(data.flatMap(item => item.subtopics))].sort();
       renderTopics();
 
       const fragment = document.createDocumentFragment();
@@ -330,11 +331,20 @@ function processData(data, filename) {
         const bigQuestionBox = document.createElement("div");
         bigQuestionBox.id = questionid;
 
-        const allClasses = [...topics.map(t => t.trim()),
-        ...subtopics.map(s => s.trim()),
+        /*const allClasses = [...topics.map(t => t.trim()),
+        subtopics,
           "hidden"];
+        bigQuestionBox.classList.add(...allClasses);*/
+
+        const allClasses = [
+            ...topics.map(t => t.trim()).filter(t => t),
+            ...(typeof subtopics === "string" ? [subtopics] : []),
+            "hidden"
+        ];
+
         bigQuestionBox.classList.add(...allClasses);
 
+
         const btnContainer = document.createElement("div");
         btnContainer.classList.add("btn-container");